RESUMEN
The U2AF Homology Motif Kinase 1 (UHMK1) is the only kinase that contains the U2AF homology motif, a common protein interaction domain among splicing factors. Through this motif, UHMK1 interacts with the splicing factors SF1 and SF3B1, known to participate in the 3' splice site recognition during the early steps of spliceosome assembly. Although UHMK1 phosphorylates these splicing factors in vitro, the involvement of UHMK1 in RNA processing has not previously been demonstrated. Here, we identify novel putative substrates of this kinase and evaluate UHMK1 contribution to overall gene expression and splicing, by integrating global phosphoproteomics, RNA-seq, and bioinformatics approaches. Upon UHMK1 modulation, 163 unique phosphosites were differentially phosphorylated in 117 proteins, of which 106 are novel potential substrates of this kinase. Gene Ontology analysis showed enrichment of terms previously associated with UHMK1 function, such as mRNA splicing, cell cycle, cell division, and microtubule organization. The majority of the annotated RNA-related proteins are components of the spliceosome but are also involved in several steps of gene expression. Comprehensive analysis of splicing showed that UHMK1 affected over 270 alternative splicing events. Moreover, splicing reporter assay further supported UHMK1 function on splicing. Overall, RNA-seq data demonstrated that UHMK1 knockdown had a minor impact on transcript expression and pointed to UHMK1 function in epithelial-mesenchymal transition. Functional assays demonstrated that UHMK1 modulation affects proliferation, colony formation, and migration. Taken together, our data implicate UHMK1 as a splicing regulatory kinase, connecting protein regulation through phosphorylation and gene expression in key cellular processes.
Asunto(s)
Proteínas Serina-Treonina Quinasas , Empalme del ARN , Empalme Alternativo , Factores de Empalme de ARN/metabolismo , Empalmosomas/genética , Empalmosomas/metabolismo , Factor de Empalme U2AF/química , Factores de Transcripción/metabolismo , Transición Epitelial-Mesenquimal , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismoRESUMEN
E. histolytica is the etiological agent of intestinal amebiasis and liver abscesses, which still poses public health threat globally. Metronidazole is the drug of choice against amebiasis. However, metronidazole-resistant amoebic clinical isolates and strains have been reported recently, challenging the efforts for amebiasis eradication. In search of alternative treatments, E. histolytica transcriptomes have shown the association of genes involved in RNA metabolism with the virulence of the parasite. Among the upregulated genes in amoebic liver abscesses are the splicing factors EhU2AF2 and a paralog of EhSF3B1. For this reason and because EhU2AF2 contains unusual KH-QUA2 (84KQ) motifs in its lengthened C-terminus domain, here we investigated how the role of EhU2AF2 in pre-mRNA processing impacts the virulence of the parasite. We found that 84KQ is involved in splicing inhibition/intron retention of several virulence and non-virulence-related genes. The 84KQ domain interacts with the same domain of the constitutive splicing factor SF1 (SF1KQ), both in solution and when SF1KQ is bound to branchpoint signal RNA probes. The 84KQ-SF1KQ interaction prevents splicing complex E to A transition, thus inhibiting splicing. Surprisingly, the deletion of the 84KQ domain in EhU2AF2 amoeba transformants increased splicing and enhanced the in vitro and in vivo virulence phenotypes. We conclude that the interaction of the 84KQ and SF1KQ domains, probably involving additional factors, tunes down Entamoeba virulence by favoring intron retention.
Asunto(s)
Entamoeba histolytica , Proteínas Protozoarias/metabolismo , Factores de Empalme de ARN/metabolismo , Animales , Disentería Amebiana/parasitología , Entamoeba histolytica/metabolismo , Entamoeba histolytica/patogenicidad , Humanos , Metronidazol , Empalme del ARN , Factor de Empalme U2AF/genética , Factor de Empalme U2AF/metabolismoAsunto(s)
Inmunidad Innata , Síndromes Mielodisplásicos/genética , Fosfoproteínas/genética , Factores de Empalme de ARN/genética , Factores de Empalme Serina-Arginina/genética , Empalmosomas/genética , Factor de Empalme U2AF/genética , Animales , Citocinas/metabolismo , Humanos , Inflamación , Células K562 , Lipopolisacáridos , Ratones , Mutación , Subunidad p50 de NF-kappa B/metabolismo , Fenotipo , Células RAW 264.7 , Empalme del ARNRESUMEN
U2 small nuclear RNA auxiliary factor 2 (U2AF2) is an important gene for pre-messenger RNA splicing in higher eukaryotes. In this study, the Banna mini-pig inbred line (BMI) U2AF2 coding sequence (CDS) was cloned, sequenced, and characterized. The U2AF2 complete CDS was amplified using the reverse transcription-polymerase chain reaction (RT-PCR) technique based on the conserved sequence information of cattle and known highly homologous swine expressed sequence tags. This novel gene was deposited into the National Center for Biotechnology Information database (Accession No. JQ839267). Sequence analysis revealed that the BMI U2AF2 coding sequence consisted of 1416 bp and encoded 471 amino acids with a molecular weight of 53.12 kDa. The protein sequence has high sequence homology with U2AF65 of 6 species - Homo sapiens (100%), Equus caballus (100%), Canis lupus (100%), Macaca mulatta (99.8%), Bos taurus (74.4%), and Mus musculus (74.4%). The phylogenetic tree analysis revealed that BMI U2AF65 has a closer genetic relationship with B. taurus U2AF65 than with U2AF65 of E. caballus, C. lupus, M. mulatta, H. sapiens, and M. musculus. RT-PCR analysis showed that BMI U2AF2 was most highly expressed in the brain; moderately expressed in the spleen, lung, muscle, and skin; and weakly expressed in the liver, kidney, and ovary. Its expression was nearly silent in the spinal cord, nerve fiber, heart, stomach, pancreas, and intestine. Three microRNA target sites were predicted in the CDS of BMI U2AF2 messenger RNA. Our results establish a foundation for further insight into this swine gene.