UBR7 functions with UBR5 in the Notch signaling pathway and is involved in a neurodevelopmental syndrome with epilepsy, ptosis, and hypothyroidism.

The ubiquitin-proteasome system facilitates the degradation of unstable or damaged proteins. UBR1-7, which are members of hundreds of E3 ubiquitin ligases, recognize and regulate the half-life of specific proteins on the basis of their N-terminal sequences ("N-end rule"). In seven individuals with intellectual disability, epilepsy, ptosis, hypothyroidism, and genital anomalies, we uncovered bi-allelic variants in UBR7. Their phenotype differs significantly from that of Johanson-Blizzard syndrome (JBS), which is caused by bi-allelic variants in UBR1, notably by the presence of epilepsy and the absence of exocrine pancreatic insufficiency and hypoplasia of nasal alae. While the mechanistic etiology of JBS remains uncertain, mutation of both Ubr1 and Ubr2 in the mouse or of the C. elegans UBR5 ortholog results in Notch signaling defects. Consistent with a potential role in Notch signaling, C. elegans ubr-7 expression partially overlaps with that of ubr-5, including in neurons, as well as the distal tip cell that plays a crucial role in signaling to germline stem cells via the Notch signaling pathway. Analysis of ubr-5 and ubr-7 single mutants and double mutants revealed genetic interactions with the Notch receptor gene glp-1 that influenced development and embryo formation. Collectively, our findings further implicate the UBR protein family and the Notch signaling pathway in a neurodevelopmental syndrome with epilepsy, ptosis, and hypothyroidism that differs from JBS. Further studies exploring a potential role in histone regulation are warranted given clinical overlap with KAT6B disorders and the interaction of UBR7 and UBR5 with histones.

The KAT6B::KANSL1 Fusion Defines a New Uterine Sarcoma With Hybrid Endometrial Stromal Tumor and Smooth Muscle Tumor Features.

Neoplasms harboring a KAT6B/A::KANSL1 fusion were initially reported as benign (leiomyomas) and malignant (leiomyosarcomas, low-grade endometrial stromal sarcomas [LG-ESSs]) uterine neoplasms. However, they may represent an emerging entity characterized by clinical aggressiveness contrasting with a rather reassuring microscopic appearance. Here, we aimed to confirm that this neoplasm is a distinct clinicopathologic and molecular sarcoma and identify criteria that should alert pathologists and lead to KAT6B/A::KANSL1 fusion testing in routine practice. Therefore, we conducted a comprehensive clinical, histopathologic, immunohistochemical, and molecular study, including array comparative genomic hybridization, whole RNA-sequencing, unsupervised clustering, and cDNA mutational profile analyses of 16 tumors with KAT6B::KANSL1 fusion from 12 patients. At presentation, patients were peri-menopausal (median, 47.5 years), and the primary tumors were located in the uterine corpus (12/12, 100%), with an additional prevesical location in 1 (8.3%) of 12 cases. The relapse rate was 33.3% (3/9). All tumors (16/16, 100%) showed morphologic and immunohistochemical features overlapping between leiomyoma and endometrial stromal tumors. A whirling recurrent architecture (resembling fibromyxoid-ESS/fibrosarcoma) was found in 13 (81.3%) of 16 tumors. All tumors (16/16, 100%) exhibited numerous arterioliform vessels, and 13 (81.3%) of 18 had large hyalinized central vessels and collagen deposits. Estrogen and progesterone receptors were expressed in 16 (100%) of 16 and 14 (87.5%) of 16 tumors, respectively. Array comparative genomic hybridization performed on 10 tumors classified these neoplasms as simple genomic sarcomas. Whole RNA-sequencing on 16 samples and clustering analysis on primary tumors found that the KAT6B::KANSL1 fusion always occurred between exons 3 of KAT6B and 11 of KANSL1; no pathogenic variant was identified on cDNA, all neoplasms clustered together, close to LG-ESS, and pathway enrichment analysis showed cell proliferation and immune infiltrate recruitment pathway involvement. These results confirm that the sarcomas harboring a KAT6B/A::KANSL1 fusion represent a distinct clinicopathologic entity, close to LG-ESS but different, with clinical aggressiveness despite a reassuring morphology, for which the KAT6B/A::KANSL1 fusion is the molecular driver alteration.

SNORD17-mediated KAT6B mRNA 2'-O-methylation regulates vasculogenic mimicry in glioblastoma cells.

Glioblastoma (GBM) is a primary tumor in the intracranial compartment. Vasculogenic mimicry (VM) is a process in which a pipeline of tumor cells that provide blood support to carcinogenic cells is formed, and studying VM could provide a new strategy for clinical targeted treatment of GBM. In the present study, we found that SNORD17 and ZNF384 were significantly upregulated and promoted VM in GBM, whereas KAT6B was downregulated and inhibited VM in GBM. RTL-P assays were performed to verify the 2'-O-methylation of KAT6B by SNORD17; IP assays were used to detect the acetylation of ZNF384 by KAT6B. In addition, the binding of ZNF384 to the promoter regions of VEGFR2 and VE-cadherin promoted transcription, as validated by chromatin immunoprecipitation and luciferase reporter assays. And finally, knockdown of SNORD17 and ZNF384 combined with KAT6B overexpression effectively reduced the xenograft tumor size, prolonged the survival time of nude mice and reduced the number of VM channels. This study reveals a novel mechanism of the SNORD17/KAT6B/ZNF384 axis in modulating VM development in GBM that may provide a new goal for the comprehensive treatment of GBM.

Resequencing the Yaroslavl cattle genomes reveals signatures of selection and a rare haplotype on BTA28 likely to be related to breed phenotypes.

The genomes of local livestock could shed light on their genetic history, mechanisms of adaptations to environments and unique genetics. Herein we look into the genetics and adaptations of the Russian native dairy Yaroslavl cattle breed using 22 resequenced individuals and comparing them with two related breeds (Russian Kholmogory and Holstein), and to the taurine set of the 1000 Bull Genomes Project (Run 9). HapFLK analysis with Kholmogory and Holstein breeds (using Yakut cattle as outgroup) resulted in 22 regions under selection (q-value < 0.01) on 11 chromosomes assigned to Yaroslavl cattle, including a strong signature of selection in the region of the KIT gene on BTA6. The FST (fixation index) with the 1000 Bull Genomes Dataset showed 48 non-overlapping top (0.1%) FST regions of which three overlapped HapFLK regions. We identified 1982 highly differentiated (FST > 0.40) missense mutations in the Yaroslavl genomes. These genes were enriched in the epidermal growth factor and calcium-binding functional categories. The top FST intervals contained eight genes with allele frequencies quite different between the Yaroslavl and Kholmogory breeds and the rest of the 1000 Bull Genomes Dataset, including KAT6B, which had a nearly Yaroslavl breed-specific deleterious missense mutation with the highest FST in our dataset (0.99). This gene is a part of a long haplotype containing other genes from FST and hapFLK analyses and with a negative association with weight and carcass traits according to the genotyping of 30 phenotyped Yaroslavl cattle individuals. Our work provides the industry with candidate genetic variants to be focused on in breed improvement efforts.

The key roles of the lysine acetyltransferases KAT6A and KAT6B in physiology and pathology.

Histone modifications and more specifically ε-lysine acylations are key epigenetic regulators that control chromatin structure and gene transcription, thereby impacting on various important cellular processes and phenotypes. Furthermore, lysine acetylation of many non-histone proteins is involved in key cellular processes including transcription, DNA damage repair, metabolism, cellular proliferation, mitosis, signal transduction, protein folding, and autophagy. Acetylation affects protein functions through multiple mechanisms including regulation of protein stability, enzymatic activity, subcellular localization, crosstalk with other post-translational modifications as well as regulation of protein-protein and protein-DNA interactions. The paralogous lysine acetyltransferases KAT6A and KAT6B which belong to the MYST family of acetyltransferases, were first discovered approximately 25 years ago. KAT6 acetyltransferases acylate both histone H3 and non-histone proteins. In this respect, KAT6 acetyltransferases play key roles in regulation of transcription, various developmental processes, maintenance of hematopoietic and neural stem cells, regulation of hematopoietic cell differentiation, cell cycle progression as well as mitosis. In the current review, we discuss the physiological functions of the acetyltransferases KAT6A and KAT6B as well as their functions under pathological conditions of aberrant expression, leading to several developmental syndromes and cancer. Importantly, both upregulation and downregulation of KAT6 proteins was shown to play a role in cancer formation, progression, and therapy resistance, suggesting that they can act as oncogenes or tumor suppressors. We also describe reciprocal regulation of expression between KAT6 proteins and several microRNAs as well as their involvement in cancer formation, progression and resistance to therapy.

Further delineation of the clinical spectrum of KAT6B disorders and allelic series of pathogenic variants.

PURPOSE: Genitopatellar syndrome and Say-Barber-Biesecker-Young-Simpson syndrome are caused by variants in the KAT6B gene and are part of a broad clinical spectrum called KAT6B disorders, whose variable expressivity is increasingly being recognized. METHODS: We herein present the phenotypes of 32 previously unreported individuals with a molecularly confirmed diagnosis of a KAT6B disorder, report 24 new pathogenic KAT6B variants, and review phenotypic information available on all published individuals with this condition. We also suggest a classification of clinical subtypes within the KAT6B disorder spectrum. RESULTS: We demonstrate that cerebral anomalies, optic nerve hypoplasia, neurobehavioral difficulties, and distal limb anomalies other than long thumbs and great toes, such as polydactyly, are more frequently observed than initially reported. Intestinal malrotation and its serious consequences can be present in affected individuals. Additionally, we identified four children with Pierre Robin sequence, four individuals who had increased nuchal translucency/cystic hygroma prenatally, and two fetuses with severe renal anomalies leading to renal failure. We also report an individual in which a pathogenic variant was inherited from a mildly affected parent. CONCLUSION: Our work provides a comprehensive review and expansion of the genotypic and phenotypic spectrum of KAT6B disorders that will assist clinicians in the assessment, counseling, and management of affected individuals.

Say-Barber-Biesecker-Young-Simpson syndrome and Genitopatellar syndrome: Lumping or splitting?

The Say-Barber-Biesecker-Young-Simpson variant of Ohdo syndrome (SBBYSS) and Genitopatellar syndrome (GTPTS) are 2 rare but clinically well-described diseases caused by de novo heterozygous sequence variants in the KAT6B gene. Both phenotypes are characterized by significant global developmental delay/intellectual disability, hypotonia, genital abnormalities, and patellar hypoplasia/agenesis. In addition, congenital heart defects, dental abnormalities, hearing loss, and thyroid anomalies are common to both phenotypes. This broad clinical overlap led some authors to propose the concept of KAT6B spectrum disorders. On the other hand, some clinical features could help to differentiate the 2 disorders. Furthermore, it is possible to establish a genotype-phenotype correlation when considering the position of the sequence variant along the gene, supporting the notion of the 2 disorders as really distinct entities.

Novel truncating variants expand the phenotypic spectrum of KAT6B-related disorders.

Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) and Genitopatellar syndrome (GTPTS) are very rare conditions caused by KAT6B truncating variants. Because of both syndromes often share common features the associated phenotypes are usually grouped under the term "KAT6B-related disorders." However, particular signs of each syndrome have been reported and their appearance seems to be dependent on where the KAT6B variant is located. Thus, whereas truncating variants associated with SBBYSS have their highest density in the distal part of exon 18, those resulting in GTPTS are distributed between the end of exon 17 and beginning of exon 18. Here, we reported two de novo heterozygous KAT6B truncating variants. The first variant (c.5802delA; p.A1935Pfs*16), identified in a boy with SSBYSS phenotype, resulting in the most distal KAT6B truncating variant reported up-to-date in the scientific literature. The second variant (c.3152delG; p.S1051Tfs*63), located in a region hitherto defined as specific of SBBYSS, seems to cause an overlapping SBBYSS/GTPTS phenotype. The clinical and genetic characterization of these patients could contribute to the understanding of the KAT6B-related disorders.

A novel truncating variant within exon 7 of KAT6B associated with features of both Say-Barber-Bieseker-Young-Simpson syndrome and genitopatellar syndrome: Further evidence of a continuum in the clinical spectrum of KAT6B-related disorders.

KAT6B sequence variants have been identified in both patients with the Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) and in the genitopatellar syndrome (GPS). In SBBYSS, they were reported to affect mostly exons 16-18 of KAT6B, and the predicted mechanism of pathogenesis was haploinsufficiency or a partial loss of protein function. Truncating variants in KAT6B leading to GPS appear to cluster within the proximal portion of exon 18, associated with a dominant-negative effect of the mutated protein, most likely. Although SBBYSS and GPS have been initially considered allelic disorders with distinctive genetic and clinical features, there is evidence that they represent two ends of a spectrum of conditions referable as KAT6B-related disorders. We detected a de novo truncating variant within exon 7 of KAT6B in a 8-year-old female who presented with mild intellectual disability, facial dysmorphisms highly consistent with SBBYSS, and skeletal anomalies including exostosis, that are usually considered component manifestations of GPS. Following the clinical diagnosis driven by the striking facial phenotype, we analyzed the KAT6B gene by NGS techniques. The present report highlights the pivotal role of clinical genetics in avoiding clear-cut genotype-phenotype categories in syndromic forms of intellectual disability. In addition, it further supports the evidence that a continuum exists within the clinical spectrum of KAT6B-associated disorders.

Complex phenotypes blur conventional borders between Say-Barber-Biesecker-Young-Simpson syndrome and genitopatellar syndrome.

Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) and genitopatellar syndrome (GTPTS) are clinically similar disorders with some overlapping features. Although they are currently considered to be distinct clinical entities, both were found to be caused by de novo truncating sequence variants in the KAT6B (lysine acetyltransferase 6B) gene, strongly suggesting that they are allelic disorders. Herein, we report the clinical and genetic findings in a girl presenting with a serious multiple congenital anomaly syndrome with phenotypic features overlapping both SBBYSS and GTPTS; pointing out that the clinical distinction between these disorders is not exact and there do exist patients, in whom conventional clinical classification is problematic. Genetic analyses revealed a truncating c.4592delA (p.Asn1531Thrfs*18) variant in the last KAT6B exon. Our findings support that phenotypes associated with typical KAT6B disease-causing variants should be referred to as 'KAT6B spectrum disorders' or 'KAT6B related disorders', rather than their current SBBYSS and GTPTS classification.

De Novo 1.77-Mb Microdeletion of 10q22.2q22.3 in a Girl With Developmental Delay, Speech Delay, Congenital Cleft Palate, and Bilateral Hearing Impairment.

Interstitial deletions of chromosome band 10q22.1q22.3 are rare. We here report a 2.5-year-old female patient with developmental delay, speech delay, congenital cleft palate, and bilateral hearing impairment. The girl's karyotype was normal. Chromosome microarray analysis (CMA) revealed a 1.77-Mb de novo interstitial deletion in 10q22.2q22.3. The deletion harbors 9 genes, including KAT6B, DUPD1, DUSP13, SAMD8, VDAC2, COMTD1, ZNF503, NCRNA00245, and C10orf11. This is the first patient with a deletion of the smallest size in 10q22.2q22.3 as detected using single nucleotide polymorphism (SNP) arrays. Comparisons with patients with overlapping deletions and in neighboring regions demonstrate the clinical impact of each deletion and in the context of other deletions within the 10q22q23 region. Additionally, KAT6B and C10orf11 could represent disease-associated genes that contribute to developmental delay, speech and language delay, and congenital cleft palate.

De Novo Mutation of KAT6B Gene Causing Atypical Say-Barber-Biesecker-Young-Simpson Syndrome or Genitopatellar Syndrome.

Mutations in KAT6B gene are responsible for Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) and genitopatellar syndrome (GPS), with most mutations occurring in exon 18. A 4-year-old Chinese boy presented with short stature but no other clinical features of SBBYSS or GPS had a de novo novel nonsense pathogenic mutation in exon 14 of the KAT6B gene at position c.2636T>A (p.Leu879X). The correlation analysis of genotype-phenotype indicated distinctive clinical features (short stature, growth hormone deficiency, and delayed bone age) compared with the classical mutations of KAT6B gene. To the best of our knowledge, this is the first report of KAT6B gene mutation in any Chinese individual. This work expands the mutant phenotypic spectrum of the KAT6B gene.

A recurrent synonymous KAT6B mutation causes Say-Barber-Biesecker/Young-Simpson syndrome by inducing aberrant splicing.

Mutations of the histone acetyltransferase-encoding KAT6B gene cause the Say-Barber-Biesecker/Young-Simpson (SBBYS) type of blepharophimosis-"mental retardation" syndromes and the more severe genitopatellar syndrome. The SBBYS syndrome-causing mutations are clustered in the large exon 18 of KAT6B and almost exclusively lead to predicted protein truncation. An atypical KAT6B mutation, a de novo synonymous variant located in exon 16 (c.3147G>A, p.(Pro1049Pro)) was previously identified in three unrelated patients. This exonic mutation was predicted in silico to cause protein truncation through aberrant splicing. Here, we report three additional unrelated children with typical SBBYS syndrome and the KAT6B c.3147G>A mutation. We show on RNA derived from patient blood that the mutation indeed induces aberrant splicing through the use of a cryptic exonic splice acceptor site created by the sequence variant. Our results thus identify the synonymous variant c.3147G>A as a splice site mutation and a mutational hot spot in SBBYS syndrome.

An individual with blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) and additional features expands the phenotype associated with mutations in KAT6B.

Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) is an autosomal dominant disorder caused by mutations in FOXL2. We identified an individual with BPES and additional phenotypic features who did not have a FOXL2 mutation. We used whole exome sequencing to identify a de novo mutation in KAT6B (lysine acetyltransferase 6B) in this individual. The mutation was a 2-bp insertion leading to a frameshift which resulted in a premature stop codon. The resulting truncated protein does not have the C-terminal serine/methionine transcription activation domain necessary for interaction with other transcriptional and epigenetic regulators. This mutation likely has a dominant-negative or gain-of-function effect, similar to those observed in other genetic disorders resulting from KAT6B mutations, including Say-Barber-Biesecker-Young-Simpson (SBBYSS) and genitopatellar syndrome (GTPTS). Thus, our subject's phenotype broadens the spectrum of clinical findings associated with mutations in KAT6B. Furthermore, our results suggest that individuals with BPES without a FOXL2 mutation should be tested for KAT6B mutations. The transcriptional and epigenetic regulation mediated by KAT6B appears crucial to early developmental processes, which when perturbed can lead to a wide spectrum of phenotypic outcomes.

The histone acetyltransferase KAT6B is required for hematopoietic stem cell development and function.

The histone lysine acetyltransferase KAT6B (MYST4, MORF, QKF) is the target of recurrent chromosomal translocations causing hematological malignancies with poor prognosis. Using Kat6b germline deletion and overexpression in mice, we determined the role of KAT6B in the hematopoietic system. We found that KAT6B sustained the fetal hematopoietic stem cell pool but did not affect viability or differentiation. KAT6B was essential for normal levels of histone H3 lysine 9 (H3K9) acetylation but not for a previously proposed target, H3K23. Compound heterozygosity of Kat6b and the closely related gene, Kat6a, abolished hematopoietic reconstitution after transplantation. KAT6B and KAT6A cooperatively promoted transcription of genes regulating hematopoiesis, including the Hoxa cluster, Pbx1, Meis1, Gata family, Erg, and Flt3. In conclusion, we identified the hematopoietic processes requiring Kat6b and showed that KAT6B and KAT6A synergistically promoted HSC development, function, and transcription. Our findings are pertinent to current clinical trials testing KAT6A/B inhibitors as cancer therapeutics.

De novo KAT6B mutation causes Say-Barber-Biesecker-Young-Simpson variant of Ohdo syndrome in an Iranian boy: a case report.

BACKGROUND: Say-Barber-Biesecker-Young-Simpson (SBBYS) (OMIM #603736, Ohdo syndrome variant) is a rare type of severe blepharophimosis intellectual disability syndrome, which is generally characterized by a global developmental delay, distinctive facial features, and intellectual disability with multiple congenital anomalies, including skeletal involvement, missing, or underdeveloped kneecaps, and genital anomalies, in affected males. It has been shown that mutations in the KAT6B gene, which is a lysine acetyltransferase-encoding gene, have been associated with SBBYS syndrome. All the known variants are dominant de novo mutations that result in protein truncation. CASE PRESENTATION: A 14-year-old Iranian Azeri boy with an intellectual disability, distinct dysmorphic facial features such as open-mouth expression, sparse medial eyebrows, widely spaced upward-slanted eyes, epicanthal folds, broad nasal bridge, low-set ears, anteverted ears, short philtrum, hypertelorism, microphthalmia is presented in this case study. Cryptorchidism was reported. Neurologically, the patient presented with poor eye contact, hypotonia, and speech difficulties. In the skeletal X-ray, underdeveloped kneecaps with some new features were observed. CONCLUSION: We present the first case of SBBYS syndrome in association with some new anomaly features in the Iranian population. Based on this diagnosis, we could provide the patient with a suitable plan of management as well as appropriate genetic counseling for his family.

Clinical heterogeneity of polish patients with KAT6B-related disorder.

BACKGROUND: Say-Barber-Biesecker-Young-Simpson (SBBYSS) variant of Ohdo syndrome is a rare, autosomal dominant and clinically heterogenous disorder, caused by pathogenic variants in the KAT6B gene located on chromosome 10q22.2. KAT6B encodes a highly conserved histone acetyltransferase belonging to the MYST family. Currently, diseases caused by pathogenic variants in KAT6B (KAT6B-related disorders) comprise two allelic entities: SBBYSS variant of Ohdo syndrome and genitopatellar syndrome (GPS). Increase in the number of cases with overlapping GPS/SBBYSS phenotype which makes it necessary to redefine this group of phenotypes as KAT6B-related disorders or KAT6B spectrum disorders. Individuals with SBBYSS usually present with facial abnormalities, hypotonia, joint laxity, feeding problems, and long thumbs/great toes. This syndrome also typically involves skeletal problems including patellar hypoplasia/agenesis. METHODS: Here we report six SBBYS syndrome patients with the same dysmorphic features but a different course of the disease. One known and five novel KATB6 pathogenic variants were identified by molecular diagnostics using Next Generation Sequencing (NGS). RESULTS: We present a detailed phenotypic analysis of six individuals with KAT6B-related disorders, in whom a heterozygous pathogenic variant in KAT6B gene was found. In all of our patients facial dysmorphism as well as developmental and speech delay were present. Additionally, all but one patients presented with hypotonia, ocular abnormalities and long thumbs. Most of our probands showed blepharophimosis and skeletal (mainly knee) defects. Contrary to previously reported severe patellar defects (hypoplasia/agenesis) anomalies presented by our patients were less severe (dysplasia, habitual dislocation, subluxation) referring to KAT6B-related disorders. CONCLUSION: While most of the anomalies found in our patients comply with SBBYSS criteria, phenotypic differences in our probands support a broader spectrum of the disease phenotype. To establish the range of this spectrum, a detailed analysis of clinical variability among patients with SBBYSS requires further investigation.

Clinical features and underlying mechanisms of KAT6B disease in a Chinese boy.

BACKGROUND: Lysine acetyltransferase 6B (KAT6B) encodes a highly conserved histone acetyltransferase that regulates the expression of multiple genes and is essential for human growth and development. METHODS: We identified a novel frameshift variant c.3185del (p.leu1062Argfs*52) in a 5-year-old Chinese boy and further analyzed KAT6B expression and its interacting complexes and downstream products using real-time quantitative polymerase chain reaction (qPCR). Furthermore, we assessed its three-dimensional protein structure and compared the variant with other reported KAT6B variants. RESULTS: The deletion changed the leucine at position 1062 into an arginine, resulting in translation termination after base 3340, which may have affected protein stability and protein-protein interactions. KAT6B mRNA expression levels in this case were substantially different from those of the parents and controls in the same age range. There were also significant differences in mRNA expression levels among affected children's parents. RUNX2 and NR5A1, downstream products of the gene, affect the corresponding clinical symptoms. The mRNA expression levels of the two in children were lower than those of their parents and controls in the same age range. CONCLUSION: This deletion in KAT6B may affect protein function and cause corresponding clinical symptoms through interactions with key complexes and downstream products.

Circ-MALAT1 accelerates cell proliferation and epithelial mesenchymal transformation of colorectal cancer through regulating miR-506-3p/KAT6B axis.

Colorectal cancer (CRC) is a prevalent malignant tumor of the digestive tract. Circular RNAs may play important roles in the progression of CRC. In this study, we investigated the roles and mechanisms of action of circ-MALAT1 in CRC. Gene expression and protein abundance were determined using qRT-PCR and western blot, respectively. Cell proliferation and migration were assessed by MTT, clone formation, and wound-healing assays. The interactions among the long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (circ-MALAT1), miR-506-3p, and lysine acetyltransferase 6B (KAT6B) were predicted using the StarBase software and confirmed by the luciferase activity assay. Circ-MALAT1 and KAT6B were upregulated, while miR-506-3p was downregulated in CRC cells. We validated that knocking down of circ-MALAT1 suppressed proliferation, migration, and epithelial-mesenchymal transition (EMT) of CRC cells, and these effects were abolished by miR-506-3p downregulation or KAT6B sufficiency. Our study suggests that circ-MALAT1 could sponge miR-506-3p to regulate the expression of KAT6B. Moreover, KAT6B sufficiency could neutralize miR-506-3p-dependent growth arrest, migration, and EMT. Circ-MALAT1 promotes cell proliferation, migration, and EMT of CRC cells via the miR-506-3p/KAT6B axis, thereby acting as a novel potential therapeutic target for the treatment of colorectal cancer.

Discovery of a highly potent, selective, orally bioavailable inhibitor of KAT6A/B histone acetyltransferases with efficacy against KAT6A-high ER+ breast cancer.

KAT6A, and its paralog KAT6B, are histone lysine acetyltransferases (HAT) that acetylate histone H3K23 and exert an oncogenic role in several tumor types including breast cancer where KAT6A is frequently amplified/overexpressed. However, pharmacologic targeting of KAT6A to achieve therapeutic benefit has been a challenge. Here we describe identification of a highly potent, selective, and orally bioavailable KAT6A/KAT6B inhibitor CTx-648 (PF-9363), derived from a benzisoxazole series, which demonstrates anti-tumor activity in correlation with H3K23Ac inhibition in KAT6A over-expressing breast cancer. Transcriptional and epigenetic profiling studies show reduced RNA Pol II binding and downregulation of genes involved in estrogen signaling, cell cycle, Myc and stem cell pathways associated with CTx-648 anti-tumor activity in ER-positive (ER+) breast cancer. CTx-648 treatment leads to potent tumor growth inhibition in ER+ breast cancer in vivo models, including models refractory to endocrine therapy, highlighting the potential for targeting KAT6A in ER+ breast cancer.