CREM: A Transcriptional Master Switch Governing the cAMP Response in the Testis
The structural organization of most transcription factors is intrinsically modular, in most cases including a DNA-binding domain and an activation domain. It has been shown that these domains can be interchanged between different factors and still retain their functional properties. This modularity suggests that during evolution, the increasing complexity of gene expression may have resulted not only by duplication and divergence of existing genes, but also by a domain shuffling process to generate factors with novel properties (Harrison 1991). An important step forward in the study of transcription factors has been the discovery that many constitute final targets of specific signal transduction pathways. The two major signal transduction systems are those including cAMP and diacylglycerol (DAG) as second messengers (Nishizuka 1986). Each pathway is also characterized by a specific protein kinase (protein kinase A (PKA) and protein kinase C (PKC), respectively) and its ultimate target DNA control element [cAMP-responsive element (CRE) and TPA-responsive element (TRE), respectively]. Although initially characterized as distinct systems, accumulating evidence points towards extensive cross-talk between these pathways (Cambier et al. 1987; Yoshimasa et al. 1987; Masquilier and Sassone-Corsi 1992).
KeywordsSertoli Cell Seminiferous Epithelium Inducible cAMP Early Repressor Adenylyl Cyclase Pathway CREM Expression
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