The PDX1 homeodomain transcription factor negatively regulates the pancreatic ductal cell-specific keratin 19 promoter
The PDX1 homeodomain transcription factor negatively regulates the pancreatic ductal cell-specific keratin 19 promoter
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DOI：
10.1074/jbc.m605891200
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发表时间：
2006-12-15
影响因子：
4.8
通讯作者：
Rustgi, Anil K.
中科院分区：
文献类型：
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作者：
Deramaudt, Therese B.;Sachdeva, Mira M.;Rustgi, Anil K.
角蛋白 19 是细胞角蛋白家族的成员，对于维持细胞结构和组织（尤其是上皮细胞）至关重要。胰腺具有三种不同的细胞类型：导管细胞、腺泡细胞和胰岛细胞，每种细胞都有不同的功能。从胚胎学角度来看，胰腺和十二指肠同源框 1 (PDX1) 同源域蛋白对于所有胰腺谱系的启动至关重要。然而，内分泌胰腺的后期分化唯一依赖于 PDX1 的高表达，而 PDX1 在导管和腺泡细胞谱系中下调。我们发现这种下调可能是细胞角蛋白 K19 正常导管表达所必需的。 K19 启动子-报告基因检测表明异位 PDX1 抑制原代胰腺导管细胞中的 K19 报告基因活性。我们的研究结果证实了这一点，即原代胰腺导管细胞中逆转录病毒介导的 PDX1 稳定转导抑制了 K19 表达，而 Min6 胰岛素瘤细胞中 PDX1 的短干扰 RNA 导致通常检测不到的 K19 的诱导。互补的功能和生化方法带来了意想不到的发现，即 PDX1 和 TALE 同源域因子家族的两个成员 MEIS1a 和 PBX1b 的多聚复合物通过 K19 转录起始位点上游的特定顺式调节元件（-341 至 -325）调节 K19 基因转录。这些数据表明，PDX1、髓系亲嗜性病毒插入位点 (MEIS) 和前 B 细胞白血病转录因子 1 (PBX) 可能在胰腺发育过程中调节导管和腺泡谱系规范。具体来说，伴随的 PDX1 抑制和 MEIS 亚型表达导致适当的导管和腺泡谱系规范。此外，PDX1 可能抑制胰腺内分泌室中的导管分化程序，特别是 β 细胞。
Keratin 19 is a member of the cytokeratin family that is critical for maintenance of cellular architecture and organization, especially of epithelia. The pancreas has three distinct cell types, ductal, acinar, and islet, each with different functions. Embryologically, the pancreatic and duodenal homeobox 1 (PDX1) homeodomain protein is critical for the initiation of all pancreatic lineages; however, the later differentiation of the endocrine pancreas is uniquely dependent upon high PDX1 expression, whereas PDX1 is down-regulated in the ductal and acinar cell lineages. We find that this down-regulation may be required for normal ductal expression of cytokeratin K19. The K19 promoter-reporter gene assay demonstrates that ectopic PDX1 inhibits K19 reporter gene activity in primary pancreatic ductal cells. This is reinforced by our findings that retrovirally mediated stable transduction of PDX1 in primary pancreatic ductal cells suppresses K19 expression, and short interfering RNA to PDX1 in Min6 insulinoma cells results in the induction of normally undetectable K19. Complementary functional and biochemical approaches led to the unexpected finding that a multimeric complex of PDX1 and two members of the TALE homeodomain factor family, MEIS1a and PBX1b, regulates K19 gene transcription through a specific cis-regulatory element (-341 to -325) upstream of the K19 transcription start site. These data suggest a unifying mechanism whereby PDX1, myeloid ecotropic viral insertion site (MEIS), and pre-B-cell leukemia transcription factor 1 ( PBX) may regulate ductal and acinar lineage specification during pancreatic development. Specifically, concomitant PDX1 suppression and MEIS isoform expression result in proper ductal and acinar lineage specification. Furthermore, PDX1 may inhibit the ductal differentiation program in the pancreatic endocrine compartment, particularly beta cells.