REDUCTION OF INSULIN GENE-TRANSCRIPTION IN HIT-T15 BETA-CELLS CHRONICALLY EXPOSED TO A SUPRAPHYSIOLOGICAL GLUCOSE-CONCENTRATION IS ASSOCIATED WITH LOSS OF STF-1 TRANSCRIPTION FACTOR EXPRESSION
REDUCTION OF INSULIN GENE-TRANSCRIPTION IN HIT-T15 BETA-CELLS CHRONICALLY EXPOSED TO A SUPRAPHYSIOLOGICAL GLUCOSE-CONCENTRATION IS ASSOCIATED WITH LOSS OF STF-1 TRANSCRIPTION FACTOR EXPRESSION
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DOI：
10.1073/pnas.92.20.9127
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发表时间：
1995-09-26
影响因子：
11.1
通讯作者：
STEIN, R
中科院分区：
文献类型：
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作者：
OLSON, LK;SHARMA, A;STEIN, R
HIT-T15 β细胞长期暴露于升高的葡萄糖浓度导致胰岛素基因转录降低，表达的降低伴随着葡萄糖敏感性转录因子结合的减少（称为GSTF），其与胰岛素基因的5'侧翼控制区内的两个富含（A+T）的元件相互作用，在这项研究中，我们研究了GSTF是否对应于最近克隆的胰岛素基因转录因子STF-1，一种同源结构域蛋白，其表达仅限于十二指肠和胰腺内胚层细胞的细胞核，我们发现，亲和纯化的抗体识别STF-1 supershift的GSTF激活剂复合物形成的HIT-T15提取物，此外，我们证明了STF-1 mRNA和蛋白水平的减少，密切相关的变化，GSTF结合在HIT-T15细胞长期培养下超生理葡萄糖浓度。这些细胞中STF-1表达的减少可以通过STF-1基因转录速率的变化来解释，这表明了转录后控制机制。为了支持这一假设，在11.1 mM葡萄糖中传代的HIT-T15细胞中没有STF-1 mRNA积累。检测到的唯一RNA物质是与5'和3' STF-1特异性cDNA探针杂交的6.4-kb STF-1 RNA物质。我们认为，6.4 kb的RNA代表STF-1 mRNA的前体，这种RNA的剪接是有缺陷的，在这些细胞，总的来说，这项研究表明，减少表达的一个关键的转录调节因子，STF-1，有助于减少胰岛素基因转录在长期培养的HIT-T15细胞在超生理葡萄糖浓度。
Chronic exposure of HIT-T15 beta cells to elevated glucose concentrations leads to decreased insulin gene transcription, The reduction in expression is accompanied by diminished binding of a glucose sensitive transcription factor (termed GSTF) that interacts with two (A+T)-rich elements within the 5' flanking control region of the insulin gene, In this study we examined whether GSTF corresponds to the recently cloned insulin gene transcription factor STF-1, a homeodomain protein whose expression is restricted to the nucleus of endodermal cells of the duodenum and pancreas, We found that an affinity-purified antibody recognizing STF-1 supershifted the GSTF activator complex formed from HIT-T15 extracts, In addition, we demonstrated a reduction in STF-1 mRNA and protein levels that closely correlated with the change in GSTF binding in HIT-T15 cells chronically cultured under supraphysiologic glucose concentrations. The reduction in STF-1 expression in these cells could be accounted for by a change in the rate of STF-1 gene transcription, suggesting a posttranscriptional control mechanism, In support of this hypothesis, no STF-1 mRNA accumulated in HIT-T15 cells passaged in 11.1 mM glucose. The only RNA species detected was a 6.4-kb STF-1 RNA species that hybridized with 5' and 3' STF-1-specific cDNA probes. We suggest that the 6.4-kb RNA represents an STF-1 mRNA precursor and that splicing of this RNA is defective in these cells, Overall, this study suggests that reduced expression of a key transcriptional regulatory factor, STF-1, contributes to the decrease in insulin gene transcription in HIT-T15 cells chronically cultured in supraphysiologic glucose concentration.