Enrichment of middle repetitive element Bm-1 transcripts in translationally active RNA fractions of the silkmoth, Bombyx mori.
The Bm-1 repetitive element family represents a group of transcribed repetitive sequences in the genome of the silkmoth Bombyx mori. In the Bm-5 and BmN permanent cell lines studied here, alpha-amanitin inhibition and nuclear 'run-on' experiments demonstrated that approximately 80% of the Bm-1 transcripts are produced by RNA polymerase II. Bm-1 transcripts are dramatically enriched in poly A+ and polysomal RNA fractions compared to total RNA in these two cell lines. In the Bm-5 cell line, from total to poly A+ and polysomal RNA fractions, Bm-1 transcripts are enriched approximately 4 and 2 times, respectively, while in the BmN cell line these same fractions are enriched about 2 and 19 times compared to total RNA. This suggests that the Bm-1 transcripts may be involved in post-transcriptional processes or control of translation. Our data also revealed less size heterogeneity of Bm-1 transcripts in polysomal as compared to nuclear fractions. In the Bm-5 and BmN cell lines, the size of most transcripts containing Bm-1 sequences increases from approximately 1700 nt in the nucleus to 3000 nt in the polysomal fraction, both fractions with RNA much larger than the Bm-1 consensus sequence (250 bp). This raises the possibility that some Bm-1 elements are transcribed as part of larger transcripts containing mRNA by way of 'read-through', and may be involved in post-transcriptional regulation of gene expression as cis and/or trans acting elements.
Department of Biological Sciences, Florida International University, Miami 33199, USA.
G P
GP
Gao
R J
RJ
Herrera
D000818:Animals; D012831:Bombyx / Q000235:genetics*; D002460:Cell Line; D005786:Gene Expression Regulation; D011061:Poly A / Q000378:metabolism; D014176:Protein Biosynthesis; D012313:RNA / Q000235:genetics* / Q000378:metabolism; D012319:RNA Polymerase II / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012091:Repetitive Sequences, Nucleic Acid
D011061:Poly A; D012313:RNA; D012319:RNA Polymerase II