PARENT SESSION
Spermatogenesis

REGULATION OF PROTAMINE EXPRESSION BY CREM AND GCNF.

Cooney, Austin¹, Hummelke, Geoffrey, ¹

ABSTRACT- The protamine genes, Prm-1 and Prm-2, are expressed specifically in post- meiotic round spermatids. The transcription factor CREM has been implicated in regulating their expression. Indeed, knock-out of CREM leads to loss of protamine expression. We have been able to recapitulate CREM regulation of protamine gene expression in a cell system. Transfection of a CREM expression vector with protamine luciferase reporters into GC1 cells leads to constitutive activation of these reporters by CREM. In contrast, transfection into JEG3 cells requires PKA activation of CREM before activation of the protamine reporters is observed. Activation by CREM is CRE dependent for Prm1. The protamine promoters contain response elements for another factor, Germ Cell Nuclear Factor (GCNF), an orphan member of the nuclear receptor superfamily. Like CREM, GCNF is expressed post-meiotically in round spermatids and is thought to regulate protamine expression. GCNF binds to response elements (DR0s) in the protamine promoters and can modulate expression in a DR0-dependent manner. GCNF represses protamine gene expression. Thus, we provide evidence that CREM is responsible for activating protamine gene expression and that GCNF is involved in turning off their expression.

KEY WORDS: GCNF, Protamines, CREM, Spermatogenesis