Walker W H, Sanborn B M, Habener J F
Laboratory of Molecular Endocrinology, Massachusetts General Hospital, Harvard Medical School, Howard Hughes Medical Institute, Boston 02114.
Proc Natl Acad Sci U S A. 1994 Dec 20;91(26):12423-7. doi: 10.1073/pnas.91.26.12423.
cAMP response element-binding protein (CREB) and modulator protein (CREM) regulate the transcription of cAMP-responsive genes via phosphorylation by cAMP-dependent protein kinase A. Reverse transcription and polymerase chain amplification of RNA from male germ cells identify an alternatively spliced CREM isoform, CREM delta C-G, lacking four exons including those encoding the protein kinase A-regulated phosphorylation domain and the flanking glutamine-rich transcriptional activation domains. CREM delta C-G retains exons that encode the basic-leucine zipper (bZIP) DNA-binding domain, binds to cAMP response elements (CREs), and competitively inhibits binding of CREB and CREM to CREs. Expression of CREM delta C-G inhibits transcription of a CRE-containing chloramphenicol acetyltransferase reporter plasmid induced by endogenous CREB. Antiserum to CREM detects CREM delta C-G in elongated spermatids from rat testis. These observations indicate that CREM delta C-G is a unique form of a competitive negative regulator of CREB-mediated gene transcription expressed in a maturation-dependent manner in haploid germ cells. The developmental specificity of CREM delta C-G suggests that it may play a role in transcriptional regulation during spermatogenesis.
环磷酸腺苷反应元件结合蛋白（CREB）和调节剂蛋白（CREM）通过依赖环磷酸腺苷的蛋白激酶A磷酸化来调节环磷酸腺苷反应基因的转录。从雄性生殖细胞中提取RNA进行逆转录和聚合酶链扩增，鉴定出一种选择性剪接的CREM异构体，即CREMδC-G，它缺少四个外显子，包括那些编码蛋白激酶A调节的磷酸化结构域和侧翼富含谷氨酰胺的转录激活结构域的外显子。CREMδC-G保留了编码碱性亮氨酸拉链（bZIP）DNA结合结构域的外显子，能与环磷酸腺苷反应元件（CRE）结合，并竞争性抑制CREB和CREM与CRE的结合。CREMδC-G的表达抑制了由内源性CREB诱导的含CRE的氯霉素乙酰转移酶报告质粒的转录。针对CREM的抗血清在大鼠睾丸的延长型精子细胞中检测到CREMδC-G。这些观察结果表明，CREMδC-G是CREB介导的基因转录的一种独特的竞争性负调节因子，以成熟依赖的方式在单倍体生殖细胞中表达。CREMδC-G的发育特异性表明它可能在精子发生过程中的转录调控中发挥作用。
