Alternative patterns of transcription and translation of the ribosomal protein L32 mRNA in somatic and spermatogenic cells in mice.
The patterns of transcription and translation of the ribosomal protein L32 (Rpl32) mRNA differ greatly in adult testis and somatic tissues. Northern blots reveal that the levels of Rpl32 mRNA are four- to five-fold higher in prepubertal and adult testes, and purified pachytene spermatocytes and round spermatids than in a variety of nongrowing adult somatic tissues. 5' RACE demonstrates that transcription in 8-day prepubertal testis, which lacks meiotic and haploid cells, strongly prefers the same start site in the 5' terminal oligopyrimidine tract (5' TOP) that is used is somatic cells. The 5' TOP is a cis element that inhibits translation of many mRNAs in nongrowing somatic cells. Although the sizes of deadenylated Rpl32 mRNAs are indistinguishable in somatic and spermatogenic cells, transcription initiates at 11 sites over a 31-nt segment in adult testis and approximately 62% of Rpl32 mRNAs lack a 5' TOP. In agreement with previous studies, low levels of cycloheximide increase the proportions and sizes of polysomes in absorbance profiles, and increase the proportions and sizes of polysomes translating four 5' TOP mRNA species including the Rpl32 mRNA in 8-day seminiferous tubules. In contrast, cycloheximide has little or no effect on the absorbance profiles and distribution of Rpl32 mRNA and 5' TOP mRNAs in adult seminiferous tubules. The failure of cycloheximide to increase the size of polysomes in adult seminiferous tubules implies a block in the pathway by which ribosomes are recruited onto translationally active mRNAs.
Kleene
Kenneth C
KC
Department of Biology, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, MA 02125-3393, USA. kenneth.kleene@umb.edu
Cataldo
Leah
L
Mastrangelo
Mary-Ann
MA
Tagne
Jean-Bosco
JB
D000375:Aging / Q000235:genetics / Q000378:metabolism; D000818:Animals; D018388:Codon, Terminator / Q000235:genetics; D003513:Cycloheximide / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D008297:Male; D051379:Mice; D011132:Polyribosomes / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis / Q000235:genetics; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D038641:RNA 5' Terminal Oligopyrimidine Sequence / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000235:genetics*; D013087:Spermatids / Q000166:cytology / Q000378:metabolism; D013090:Spermatocytes / Q000166:cytology / Q000378:metabolism*; D013091:Spermatogenesis / Q000235:genetics*; D013737:Testis / Q000166:cytology / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics
D018388:Codon, Terminator; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D012269:Ribosomal Proteins; C041806:ribosomal protein L32; D003513:Cycloheximide