Histoautoradiographic study of rRNA and mRNA transcription activity related to secretory function in lizard epididymis.

Abstract

The lizard epididymis is an androgen-dependent organ whose epithelial cells undergo marked changes in structure and secretory activity during the annual cycle. These changes are connected to fluctuations of testosterone levels. During the breeding season, the epididymis produces a major protein secretion, the L-proteins. In the present work we studied the fluctuations of RNA synthesis and accumulation during the annual cycle by means of histoautoradiographic methods. Total RNA synthesis was determined by uridine incorporation; accumulation of rRNAs and L-protein mRNAs were determined by in situ hybridization. Total RNA synthesis began during reorganization (Phase I), then increased gradually during differentiation and growth (Phase II). The synthesis peaked during maturation (Phase III), but stopped abruptly during hypersecretory activity (Phase IV). The rRNAs were very abundant from Phase II to Phase IV, which is related to the presence of many ribosomes as revealed by electron microscopy. The mRNAs of L-proteins were detected only during Phases III and IV in all epithelial cells. For every phase of the sexual cycle there exists a strong correspondence between the changes in transcriptional activity (rRNA and specific mRNA) of the epithelial cells and changes in the testosterone levels.

Is Poly(A) Tail Length Altered by Aging or Dietary Restriction?

“…Our results argue strongly against an age-related defect in three critical areas of cellular metabolism: the production of mRNA (RNA polymerase II activity), the production of rRNA (RNA polymerase I ac tivity) and the production of ribosomal pro teins (which would otherwise be expected to limit the production of rRNA). It should be noted that any of these three steps could be limiting the other two, but the ability of organisms to shift this ratio [25] argues that the basal values do not serve as limits. This alters the focus of a potential cause of the observed decrease in gene expression away from factors involved in the transcription of all genes toward those factors that are respon sible for regulating the expression of specific genes.…”