A developmental switch in transcription factor isoforms during spermatogenesis controlled by alternative messenger RNA 3'-end formation.
Spermatogeniccells elaborate a highly specialized differentiation program that is mediated in part by germ cell-enriched transcription factors. This includes a novel member of the sterol response element-binding factor family, SREBF2_v1/SREBP2gc. Somatic SREBFs are predominantly synthesized as precursor proteins and are critical regulators of cholesterol and fatty acid synthesis. In contrast, SREBF2_v1 bypasses the precursor pathway and has been directly implicated in spermatogenic cell-specific gene expression. During spermatogenesis, SREBF2 precursor transcripts predominate in premeiotic stages, while SREBF2_v1 is highly upregulated specifically in pachytene spermatocytes and round spermatids. In the present study, we demonstrate thatSrebf2_v1mRNAs are present in the testis of several mammalian species, including humans. The basis for the stage-dependent transition in SREBF2 isoforms was also investigated. A 3' rapid amplification of cDNA ends (RACE)-PCR analysis of the rat and human revealed thatSrebf2_v1transcripts are generated by alternative pre-mRNA cleavage/polyadenylation. This involves the use of an intronic, A(A/U)UAAA-independent poly(A) signal within intron 7 of theSrebf2gene. Developmentally regulated competition between germ cell factors that control RNA splicing and pre-mRNA cleavage/polyadenylation may underlie this process. These results define an important role for alternative polyadenylation in male germ cell gene expression and development by controlling a stage-dependent switch in transcription factor structure and function during spermatogenesis. TheSrebf2gene thus provides a useful model to explore the role of alternative polyadenylation in regulating stage-dependent functions of important protein regulators in spermatogenic cells.
Wang
Hang
H
Department of Molecular and Cellular Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
Sartini
Becky L
BL
Millette
Clarke F
CF
Kilpatrick
Daniel L
DL
D017398:Alternative Splicing / Q000502:physiology*; D000818:Animals; D015152:Blotting, Northern; D006224:Cricetinae; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008540:Meiosis / Q000502:physiology; D051379:Mice; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D026721:RNA 3' End Processing / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013091:Spermatogenesis / Q000502:physiology*; D051782:Sterol Regulatory Element Binding Protein 2 / Q000235:genetics*; D051779:Sterol Regulatory Element Binding Proteins / Q000235:genetics*; D013737:Testis / Q000378:metabolism
C497390:SREBF2 protein, human; C470194:Srebf2 protein, rat; D051782:Sterol Regulatory Element Binding Protein 2; D051779:Sterol Regulatory Element Binding Proteins; D012313:RNA