Publisher Correction: DNA damage detection in nucleosomes involves DNA register shifting.

In this Article, in Fig. 1a, the 5' and 3' labels were reversed in the DNA sequence, and Fig. 4 was missing panel labels a-e. These errors have been corrected online.

DNA damage detection in nucleosomes involves DNA register shifting.

Access to DNA packaged in nucleosomes is critical for gene regulation, DNA replication and DNA repair. In humans, the UV-damaged DNA-binding protein (UV-DDB) complex detects UV-light-induced pyrimidine dimers throughout the genome; however, it remains unknown how these lesions are recognized in chromatin, in which nucleosomes restrict access to DNA. Here we report cryo-electron microscopy structures of UV-DDB bound to nucleosomes bearing a 6-4 pyrimidine-pyrimidone dimer or a DNA-damage mimic in various positions. We find that UV-DDB binds UV-damaged nucleosomes at lesions located in the solvent-facing minor groove without affecting the overall nucleosome architecture. In the case of buried lesions that face the histone core, UV-DDB changes the predominant translational register of the nucleosome and selectively binds the lesion in an accessible, exposed position. Our findings explain how UV-DDB detects occluded lesions in strongly positioned nucleosomes, and identify slide-assisted site exposure as a mechanism by which high-affinity DNA-binding proteins can access otherwise occluded sites in nucleosomal DNA.

Repair of topoisomerase 1-induced DNA damage by tyrosyl-DNA phosphodiesterase 2 (TDP2) is dependent on its magnesium binding.

Topoisomerases are enzymes that relax DNA supercoiling during replication and transcription. Camptothecin, a topoisomerase 1 (TOP1) inhibitor, and its analogs trap TOP1 at the 3'-end of DNA as a DNA-bound intermediate, resulting in DNA damage that can kill cells. Drugs with this mechanism of action are widely used to treat cancers. It has previously been shown that tyrosyl-DNA phosphodiesterase 1 (TDP1) repairs TOP1-induced DNA damage generated by camptothecin. In addition, tyrosyl-DNA phosphodiesterase 2 (TDP2) plays critical roles in repairing topoisomerase 2 (TOP2)-induced DNA damage at the 5'-end of DNA and in promoting the repair of TOP1-induced DNA damage in the absence of TDP1. However, the catalytic mechanism by which TDP2 processes TOP1-induced DNA damage has not been elucidated. In this study, we found that a similar catalytic mechanism underlies the repair of TOP1- and TOP2-induced DNA damage by TDP2, with Mg2+-TDP2 binding playing a role in both repair mechanisms. We show chain-terminating nucleoside analogs are incorporated into DNA at the 3'-end and abort DNA replication to kill cells. Furthermore, we found that Mg2+-TDP2 binding also contributes to the repair of incorporated chain-terminating nucleoside analogs. Overall, these findings reveal the role played by Mg2+-TDP2 binding in the repair of both 3'- and 5'-blocking DNA damage.

Anamorelin Induced Acute Hyperglycemia in a Patient with Advanced Pancreatic Cancer and Diabetes: A Case Report.

Anamorelin (ANAM) is a novel ghrelin receptor agonist for the treatment of cancer cachexia. In clinical trials of ANAM, glucose metabolism disorders as adverse effects were relatively frequent, however, when and how they occur remains unclear. Moreover, the safety in patients with pancreatic cancer and/or diabetes has not been clarified because most previous studies focused on patients with non-small cell lung cancer and had excluded patients with poorly controlled diabetes. Herein, a 66-year-old man with advanced pancreatic cancer and diabetes was administered ANAM, and acute hyperglycemia was developed and could be monitored by the self-monitoring of blood glucose (SMBG). Increasing the insulin dose failed to control hyperglycemia adequately, but the hyperglycemia ameliorated quickly after ANAM discontinuation. The continuous glucose monitoring (CGM) revealed that the sensor glucose levels had remained in the high range throughout the day during ANAM administration despite using 1.5 times more insulin. Our report is one of the few that describe the details of ANAM-induced hyperglycemia and provides important information for the safe and effective use of ANAM.

Validity and reproducibility of the intake of trans-fatty acids estimated using a FFQ and characteristics of trans-fatty acid intake of the Japanese population: the JPHC FFQ Validation Study.

We aimed to validate a method for assessing trans-fatty acid (TFA) intake in the Japanese population using the FFQ developed in the 1990s from a prospective study that was based on the Japan Public Health Center-based Prospective Cohort Study. For FFQ validation, we included 565 participants (Cohort I: n 215, Cohort II: n 350) aged 40-69 years. We used a 28-d dietary record (DR) over 1 year and two FFQ administered before and after DR assessment. We calculated total TFA intake, TFA from industrial oils (i-TFA) and TFA from ruminants (r-TFA) considering a database of measurements obtained mainly from Japan. Spearman's rank correlation coefficients (CC) were computed for validity and reproducibility. Energy adjustments were applied using two methods considering the TFA measurement: density method for TFA % of total energy and residual method for TFA g/d. The total TFA intake (% of the total energy intake) was 0·08-0·76 % (median, 0·27-0·37 %) in DR of both cohorts and was 0·00-1·13 % (median, 0·30-0·40 %) in FFQ. The i-TFA accounted for approximately 50 % of the total TFA intake in DR and approximately 40 % in FFQ. For total TFA (% of the total energy intake), CC were 0·54-0·69, and weighted κ coefficients were 0·88-0·92 for both cohorts. The de-attenuated CC was 0·46-0·62 for i-TFA (g/d) and 0·57-0·68 for r-TFA (g/d). Our study showed that the validity and reproducibility of TFA intake estimation using the FFQ were reasonable, suggesting its suitability among the Japanese population with low-TFA intake.

[How to Repair the Bicuspid Aortic Valve Accompanying Regurgitation?]

We repaired the bicuspid aoric valve( BAV) with aortic regurgitation( AR) by bicuspidization. However, repaired fused cusp does not open full, and shows doming. Between 1997 and 2023 we repaired 30 BAV with AR. Mean Age was 44( 15-79) years old. Male gender was 26/30. Between 1997 and 2017, we repaired by triangular resection and cusp suspension or central plication and the commissural positions remained as it was, in 17 cases. Between 2018 and 2023, we repaired by triangular resection and aortic root remodeling to make the commissure angle 180 degree in 13 cases. One patient died because of compression occlusion of left main trunk by Schaefer's annulplasty suture post-operatively. Postoperative aortic valve pressure gradient was 12.2±5.4 mmHg in natural commissure position group, 14.7±6.8 mmHg in the 180 degree commissure position group( p=0.37). And in the 180 degree commissure position group, the fused cusp did not show doming. In the 180 degree commissure position group, the fused cusp did not show doming. However, trans aortic valve pressure gradient did not decrease. On the other hand, in the natural commissure group, the fused cusp showed doming. However, the valves well functioned up to 25 years without aortic stenosis.

[Mitral Valve Plasty for Complicated Lesions with Barlow-like Anterior Leaflet].

A 66 year-old male was admitted to our clinic suffering from dyspnea on effort. Cardio thoracic ratio (CTR) was 62%. Electrocardiogram showed atrial fibrillation. Echocardiogram showed severe mitral regurgitation (MR), Barlow like billowing and thickened A2 and A3, and loss of P2 and P3. Operation was performed through median sternotomy and right sided left atrial incision. Left atrial appendage was closed with running suture. Maze operation was done. Triangular resection of A2 and A3 was done. P2 and P3 were adhered to the left ventricular wall. First we cut the adhered posterior leaflet in a shape of inverted T. And the adhered leaflet was dissected from the left ventricle by the scissors. The detached annulus was mattress-sutured with a pledgetted suture. The leaflets were sutured together, then a new posterior leaflet was remade using mitral valve leaflet tissue and the shape became higher and round. Post operatively, MR was none, and posterior leaflet functioned well. Sinus rhythm was recovered. Eleven years later, no MR and sinus rhythm were shown.

Enhanced DNA repair by DNA photolyase bearing an artificial light-harvesting chromophore.

Photolyases are flavoenzymes responsible for the repair of carcinogenic DNA damage caused by ultraviolet radiation. They harbor the catalytic cofactor flavin adenine dinucleotide (FAD). The light-driven electron transfer from the excited state of the fully-reduced form of FAD to the DNA lesions causes rearrangement of the covalent bonds, leading to the restoration of intact nucleobases. In addition to the catalytic chromophore, some photolyases bear a secondary chromophore with better light absorption capability than FAD, acting as a light-harvesting chromophore that harvests photons in sunlight efficiently and transfers light energy to the catalytic center, as observed in natural photoreceptor proteins. Inspired by nature, we covalently and site-specifically attached a synthetic chromophore to the surface of photolyase using oligonucleotides containing a modified nucleoside and a cyclobutane-type DNA lesion, and successfully enhanced its enzymatic activity in the light-driven DNA repair. Peptide mapping in combination with theoretical calculations identified the amino acid residue that binds to the chromophore, working as an artificial light-harvesting chromophore. Our results broaden the strategies for protein engineering and provide a guideline for tuning of the light perception abilities and enzymatic activity of the photoreceptor proteins.

Structural Changes during the Photorepair and Binding Processes of Xenopus (6-4) Photolyase with (6-4) Photoproducts in Single- and Double-Stranded DNA.

Photolyases (PHRs) repair ultraviolet (UV)-induced DNA photoproducts into normal bases. In this study, we measured the conformational changes upon photoactivation and photorepair processes of a PHR and its specific substrates, (6-4)PHR and a pyrimidine(6-4)pyrimidone photoproduct ((6-4)PP), by light-induced difference Fourier transform infrared (FT-IR) spectroscopy. The single-stranded DNA with (6-4)PP (ss(6-4)PP) was used as a substrate and the resultant FT-IR spectra were compared with the previous results on double-stranded DNA with (6-4)PP (ds(6-4)PP). In the excess amount of substrate to the enzyme, different ss(6-4)PP photorepair FT-IR signals were obtained in an illumination time-dependent manner. As reported for ds(6-4)PP, the early stages of the photoreaction involve the changes in the ss(6-4)PP only, while the late stages of the reaction involve the ss(6-4)PP repair-associated changes and dissociation from (6-4)PHR. From these spectra, difference spectra originating from the binding/dissociation spectrum were extracted. The signals of the C═O stretches of (6-4)PP and repaired thymines in the single- and double-stranded DNA were tentatively assigned. The C═O stretches of (6-4)PP were observed at frequencies that reflect single- and double-stranded DNA environments in aqueous solution, reflecting the different hydrogen-bonding environments. The conformational changes of PHR upon binding of ss(6-4)PP and ds(6-4)PP were similar, suggesting that the conformational change is limited to the (6-4)PP binding pocket region. We interpreted that ds(6-4)PP may be bound together without any special mechanism for flipping out.

Key interactions with deazariboflavin cofactor for light-driven energy transfer in Xenopus (6-4) photolyase.

Photolyases are flavoenzymes responsible for light-driven repair of carcinogenic crosslinks formed in DNA by UV exposure. They possess two non-covalently bound chromophores: flavin adenine dinucleotide (FAD) as a catalytic center and an auxiliary antenna chromophore that harvests photons and transfers solar energy to the catalytic center. Although the energy transfer reaction has been characterized by time-resolved spectroscopy, it is strikingly important to understand how well natural biological systems organize the chromophores for the efficient energy transfer. Here, we comprehensively characterized the binding of 8-hydroxy-7,8-didemethyl-5-deazariboflavin (8-HDF) to Xenopus (6-4) photolyase. In silico simulations indicated that a hydrophobic amino acid residue located at the entrance of the binding site dominates translocation of a loop upon binding of 8-HDF, and a mutation of this residue caused dysfunction of the efficient energy transfer in the DNA repair reaction. Mutational analyses of the protein combined with modification of the chromophore suggested that Coulombic interactions between positively charged residues in the protein and the phenoxide moiety in 8-HDF play a key role in accommodation of 8-HDF in the proper direction. This study provides a clear evidence that Xenopus (6-4) photolyase can utilize 8-HDF as the light-harvesting chromophore. The obtained new insights into binding of the natural antenna molecule will be helpful for the development of artificial light-harvesting chromophores and future characterization of the energy transfer in (6-4) photolyase by spectroscopic studies.

Plant organellar DNA polymerases bypass thymine glycol using two conserved lysine residues.

Plant organelles cope with endogenous DNA damaging agents, byproducts of respiration and photosynthesis, and exogenous agents like ultraviolet light. Plant organellar DNA polymerases (DNAPs) are not phylogenetically related to yeast and metazoan DNAPs and they harbor three insertions not present in any other DNAPs. Plant organellar DNAPs from Arabidopsis thaliana (AtPolIA and AtPolIB) are translesion synthesis (TLS) DNAPs able to bypass abasic sites, a lesion that poses a strong block to replicative polymerases. Besides abasic sites, reactive oxidative species and ionizing radiation react with thymine resulting in thymine glycol (Tg), a DNA adduct that is also a strong block to replication. Here, we report that AtPolIA and AtPolIB bypass Tg by inserting an adenine opposite the lesion and efficiently extend from a Tg-A base pair. The TLS ability of AtPolIB is mapped to two conserved lysine residues: K593 and K866. Residue K593 is situated in insertion 1 and K866 is in insertion 3. With basis on the location of both insertions on a structural model of AtPolIIB, we hypothesize that the two positively charged residues interact to form a clamp around the primer-template. In contrast with nuclear and bacterial replication, where lesion bypass involves an interplay between TLS and replicative DNA polymerases, we postulate that plant organellar DNAPs evolved to exert replicative and TLS activities.

Association Between Okinawan Vegetables Consumption and Risk of Type 2 Diabetes in Japanese Communities: The JPHC Study.

BACKGROUND: Some Okinawan vegetables have been reported to have anti-diabetic activity; however, no prospective cohort study has clarified whether consumption of Okinawan vegetables is associated with a risk of type 2 diabetes. This study aimed to determine the association between consumption of Okinawan vegetables and risk of type 2 diabetes through a large-scale, population-based, prospective study in Japan. METHODS: We examined 10,732 participants (4,714 men and 6,018 women) aged 45-74 years who resided in Okinawa. Participants were asked to answer a 147-item food frequency questionnaire. We calculated the overall amount of Okinawan vegetables consumed and the amount of seven specific kinds of Okinawan vegetables consumed. The odds ratios (ORs) for self-reported type 2 diabetes during 5 years of follow-up were estimated via multivariate logistic regression analysis. RESULTS: During the 5-year period, 216 new cases (123 men and 93 women) of type 2 diabetes were reported. Comparing the highest tertile to the lowest tertile of intake, the overall amount of Okinawan vegetables consumed was not associated with risk of type 2 diabetes in men (OR 1.22; 95% confidence interval [CI], 0.74-2.01, P-trend = 0.53) or in women (OR 0.96; 95% CI, 0.57-1.62, P-trend = 0.89). The consumption of seven specific kinds of Okinawan vegetables was also not associated with the risk of type 2 diabetes. CONCLUSIONS: The consumption of total Okinawan vegetables was not associated with the risk of type 2 diabetes.

Association of Vegetable, Fruit, and Okinawan Vegetable Consumption With Incident Stroke and Coronary Heart Disease.

BACKGROUND: Few studies have investigated the effects of Okinawan vegetable consumption on the risk of incident stroke and coronary heart disease. This study aimed to examine associations of vegetable, fruit, and Okinawan vegetable consumption with risk of incident stroke and coronary heart disease in the Japanese population of Okinawa. METHODS: The study design was a prospective cohort study. During 1995-1998, a validated food frequency questionnaire was administered in two study areas to 16,498 participants aged 45-74 years. In 217,467 person-years of follow-up until the end of 2012, a total of 839 stroke cases and 197 coronary heart disease cases were identified. RESULTS: No statistically significant association between total Okinawan vegetable consumption and risk of stroke and coronary heart disease was obtained: the multivariable adjusted hazard ratios for the highest versus lowest tertile of consumption were 1.09 (95% confidence interval, 0.93-1.29; P for trend = 0.289) in model 2. Total vegetable and fruit and specific Okinawan vegetable consumption were also not statistically significantly associated with risk of cardiovascular outcomes. CONCLUSIONS: This study demonstrated that consumption of total vegetable and fruit, total Okinawan vegetables, and specific Okinawan vegetables in Japanese residents of Okinawa was not associated with risk of incident stroke and coronary heart disease.

Variations in the estimated intake of acrylamide from food in the Japanese population.

BACKGROUND: Due to concerns of carcinogenicity, it is necessary to assess long-term acrylamide exposure in individuals. Whether the available methods of estimating acrylamide intake can indicate long-term exposure remains unknown. We examined variations in the estimated dietary acrylamide intake of the Japanese population. METHODS: The study included 240 participants aged 40-74 years who were a part of the Japan Public Health Center-based Prospective Study for the Next Generation (JPHC-NEXT). Twelve-day dietary records (DRs) were collected over a one-year period, and food frequency questionnaires (FFQs) were collected twice during the year. Dietary acrylamide intake was estimated from an acrylamide content database. Within-individual variations and between-individual variations were calculated using the random effects model. A linear regression analysis was performed to identify foods with large between-individual variations. RESULTS: The ratios of within-individual variance to between-individual variation were 3.2 for men and 4.3 for women. Days of DRs required to estimate the usual individual intake within 20% of the true mean intake with 95% confidence were 60 days for men and 66 days for women. Coffee/cocoa, potato, and green tea contributed to between-individual variations, in that order, and seven foods contributed to 93% of the between-individual variation. CONCLUSIONS: Estimating the acrylamide intake using DRs requires an extended data collection period to estimate the intragroup ranking and habitual intake of individuals. Long-term exposure assessments should be based on methods with less potential for measurement errors, such as the use of biomarkers.

Structure of the bifunctional cryptochrome aCRY from Chlamydomonas reinhardtii.

Photolyases and cryptochromes form an almost ubiquitous family of blue light photoreceptors involved in the repair and maintenance of DNA integrity or regulatory control. We found that one cryptochrome from the green alga Chlamydomonas reinhardtii (CraCRY) is capable of both, control of transcript levels and the sexual cycle of the alga in a positive (germination) and negative manner (mating ability), as well as catalyzing the repair of UV-DNA lesions. Its 1.6 Å crystal structure shows besides the FAD chromophore an aromatic tetrad that is indispensable in animal-like type I cryptochromes for light-driven change of their signaling-active redox state and formation of a stable radical pair. Given CraCRY's catalytic activity as (6-4) photolyase in vivo and in vitro, we present the first co-crystal structure of a cryptochrome with duplex DNA comprising a (6-4) pyrimidine-pyrimidone lesion. This 2.9 Å structure reveals a distinct conformation for the catalytic histidine His1, H357, that challenges previous models of a single-photon driven (6-4) photolyase mechanism.

Coulomb and CH-π interactions in (6-4) photolyase-DNA complex dominate DNA binding and repair abilities.

(6-4) Photolyases ((6-4)PLs) are flavoenzymes that repair the carcinogenic UV-induced DNA damage, pyrimidine(6-4)pyrimidone photoproducts ((6-4)PPs), in a light-dependent manner. Although the reaction mechanism of DNA photorepair by (6-4)PLs has been intensively investigated, the molecular mechanism of the lesion recognition remains obscure. We show that a well-conserved arginine residue in Xenopus laevis (6-4)PL (Xl64) participates in DNA binding, through Coulomb and CH-π interactions. Fragment molecular orbital calculations estimated attractive interaction energies of -80-100 kcal mol-1 for the Coulomb interaction and -6 kcal mol-1 for the CH-π interaction, and the loss of either of them significantly reduced the affinity for (6-4)PP-containing oligonucleotides, as well as the quantum yield of DNA photorepair. From experimental and theoretical observations, we formulated a DNA binding model of (6-4)PLs. Based on the binding model, we mutated this Arg in Xl64 to His, which is well conserved among the animal cryptochromes (CRYs), and found that the CRY-type mutant exhibited reduced affinity for the (6-4)PP-containing oligonucleotides, implying the possible molecular origin of the functional diversity of the photolyase/cryptochrome superfamily.

Enhancement of postprandial endogenous insulin secretion rather than exogenous insulin injection ameliorated insulin antibody-induced unstable diabetes: a case report.

BACKGROUND: Insulin injection, especially with insulin analogs, occasionally induces the production of insulin antibodies with high binding capacity and low affinity, similar to the insulin autoantibodies characteristic of insulin autoimmune syndrome (IAS). Production of these "IAS-like" insulin antibodies causes marked glycemic fluctuations with postprandial hyperglycemia and fasting hypoglycemia. CASE PRESENTATION: A 66-year-old man with a 27-year history of diabetes was admitted because of marked glycemic fluctuations. Human insulin treatment had been initiated at age 56, followed by multiple daily injections of insulin analogs 5 years later. After the initial year of insulin analog treatment, the patient began to experience frequent morning hypoglycemic attacks and day-time hyperglycemia. Marked hyperinsulinemia (4500 µU/mL) and high titers of insulin antibodies (80.4%) with high binding capacity and low affinity indicated that IAS-like insulin antibodies were causing severe glucose fluctuations. Altering insulin formulations (insulin aspart → regular human insulin→ insulin lispro) proved to be ineffective. After several therapeutic trials, cessation of exogenous insulin and addition of mitiglinide to liraglutide with voglibose finally attenuated glycemic fluctuations with increased postprandial insulin secretion. Continuous glucose monitoring revealed improvement of morning hypoglycemia and postprandial hyperglycemia with smaller mean amplitude of glycemic excursion. Therefore, compared to exogenously injected insulin, endogenously secreted insulin directly and rapidly acts on hepatocytes and suppresses postprandial glucose output. CONCLUSIONS: Proper enhancement of postprandial endogenous insulin aimed at suppressing postprandial glucose output without stimulating excessive glucose uptake in the periphery is potentially useful for treating diabetes with insulin antibody-induced glycemic instability.

Antidiabetic-Like Effects of Naringenin-7-O-glucoside from Edible Chrysanthemum 'Kotobuki' and Naringenin by Activation of the PI3K/Akt Pathway and PPARγ.

Obesity is directly associated with cancer, cardiovascular injury, hypertension, and type 2 diabetes. To date, Yamamoto identified that hot water extracts of edible Chrysanthemum (EC) induced cell size reduction, up-regulation of adiponectin expression, and glucose absorption inhibition in 3T3-L1 cells during adipocyte differentiation. Furthermore, EC showed antidiabetic effects such as improvement in insulin resistance and the down-regulation of the blood glucose level and liver lipid content in type 2 diabetes model mice. In this study, we attempted to identify the antidiabetic components in EC. The methanol fraction from EC that showed relatively strong biological activity was purified by chromatography to obtain acacetin-7-O-glucoside, apigenin-7-O-glucoside, kaempferol-7-O-glucoside, and naringenin-7-O-glucoside. Among the isolated compounds and their aglycones, naringenin (NA) and naringenin-7-O-glucoside (NAG) up-regulated the intracellular accumulation of lipid and adiponectin-secretion and down-regulated the diameter of 3T3-L1 cells during adipocyte differentiation. Because the PPARγ antagonist BADGE and PI3K/Akt inhibitors wortmannin and LY29004 inhibited the intracellular lipid accumulation by NA and NAG associated with adipogenesis, it was considered that NA and NAG showed the above-mentioned activities via the activation of PPARγ as well as phosphorylation of the PI3K/Akt pathway.

Loss of Fourth Electron-Transferring Tryptophan in Animal (6-4) Photolyase Impairs DNA Repair Activity in Bacterial Cells.

(6-4) photolyases [(6-4)PLs] are flavoproteins that use blue light to repair the ultraviolet-induced pyrimidine(6-4)pyrimidone photoproduct in DNA. Their flavin adenine dinucleotide (FAD) cofactor can be reduced to its repair-active FADH- form by a photoinduced electron transfer reaction. In animal (6-4)PLs, a chain of four Trp residues was suggested to be involved in a stepwise transfer of an oxidation hole from the flavin to the surface of the protein. Here, we investigated the effect of mutation of the fourth Trp on the DNA photorepair activity of Xenopus laevis (6-4)PL (Xl64) in bacterial cells. The photoreduction and photorepair properties of this mutant protein were independently characterized in vitro. Our results demonstrate that the mutation of the fourth Trp in Xl64 drastically impairs the DNA repair activity in cells and that this effect is due to the inhibition of the photoreduction process. We thereby show that the photoreductive formation of FADH- through the Trp tetrad is essential for the biological function of the animal (6-4)PL. The role of the Trp cascade, and of the fourth Trp in particular, is discussed.

Suppression of lethal-7b and miR-125a/b Maturation by Lin28b Enables Maintenance of Stem Cell Properties in Hepatoblasts.

UNLABELLED: In liver development, hepatoblasts that act as hepatic stem/progenitor cells proliferate and differentiate into both hepatocytes and cholangiocytes to form liver tissues. Although numerous factors contribute to this event, little is known about the roles of microRNAs in hepatoblast proliferation and differentiation. In this study, we focused on the lineage-28 (Lin28) family proteins, which are required for microRNA regulation in pluripotent stem cells and cancer cells, and investigated their roles as regulatory factors for the properties of hepatoblasts. CONCLUSION: Lin28b was specifically expressed in hepatoblasts, and its suppression induced growth arrest and cholangiocyte differentiation of hepatoblasts; mechanistically, Lin28b positively regulates the expression of Lin28b itself and cell cycle-related proteins in hepatoblasts by suppressing the maturation of target microRNAs, lethal-7b and miR-125a/b, enabling maintenance of the stem cell properties of hepatoblasts, such as their capabilities for proliferation and bi-lineage differentiation, during liver development. (Hepatology 2016;64:245-260).