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Regulation of cyclic adenosine 3',5'-monophosphate response element binding protein (CREB) expression by Sp1 in the

Scott A Shell1, Charity Fix, Donna Olejniczak

  • 1Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.

Biology of Reproduction
|March 1, 2002
PubMed

Insights

This study reveals that the transcription factor Sp1 and a novel regulatory element are crucial for activating CREB gene expression in mammalian testis germ cells during specific developmental stages.

Area of Science:

  • Reproductive Biology
  • Molecular Endocrinology
  • Spermatogenesis Regulation

Background:

  • Follicle-stimulating hormone (FSH) activates cAMP signaling in Sertoli cells, leading to CREB phosphorylation.
  • CREB gene expression in Sertoli cells is cAMP-inducible, requiring specific DNA elements (CREs) and Sp1 binding sites.
  • CREB expression patterns and regulation in mammalian testis germ cells remain incompletely understood.

Purpose of the Study:

  • To investigate the expression of CREB and Sp1 in testis germ cells during spermatogenesis.
  • To identify regulatory elements and factors controlling CREB gene expression in germ cells.
  • To elucidate the roles of Sp1 and novel regulatory regions in CREB promoter activity.

Main Methods:

  • Immunohistochemical analysis to determine CREB and Sp1 expression in germ cells.
  • Reporter gene assays in SL2 cells to assess CREB promoter activity.
  • Site-directed mutagenesis and protein binding studies to characterize promoter elements and interactions.

Main Results:

  • CREB and Sp1 are expressed in early germ cells up to the mid-pachytene stage.
  • Sp1 overexpression significantly induces CREB promoter activity (>70-fold) in SL2 cells.
  • A novel regulatory element (-130 region) is identified, essential for full CREB promoter activity.
  • Proteins from both Sertoli and germ cells specifically bind to this newly identified regulatory region.

Conclusions:

  • Sp1 is a key regulator of CREB expression in mammalian testis germ cells.
  • A previously unrecognized regulatory element in the CREB promoter is critical for its activation.
  • Coordinated action of Sp1-binding motifs and proteins interacting with the -130 region is necessary for CREB promoter activation during spermatogenesis.

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