| Summary: | Bm-1 repetitive element family represents a group of sequences in the genome of the silkmoth, Bombyx mori. and is found to be transcribed. There are about 3X more Bm-1 cytoplasmic transcripts as compared to their nuclear counterparts. The size range of Bm-1 nuclear transcripts is greater than that of their cytoplasmic species. Alpha- amanitin inhibition and nuclear ”run-on” experiments demonstrated that 80-85% of the Bm-1 transcripts are produced by RNA polymerase II; the other 15-20% may be transcribed by polymerase I and/or III. Sharply contrasting with most of the transcribed SINE families, the Bm-1 transcripts are dramatically enriched in both poly A+ and polysomal RNA fractions. Compared to Bm-1 transcripts in total RNA there are 2-4X more Bm-1 transcripts in the poly A+ RNA population and up to 22X more in the polysomal RNA fractions. This strongly suggests that the transcripts of the Bm-1 family may be involved in translation. To express exogenous Bm-1 elements in vivo and explore their effect(s) on transcriptional actitivity in Bombyx mori cells in culture and their possible function in gene regulation, two members of the Bm-1 family, clone 1 and clone 10, have been subcloned into a selectable and inducible plasmid vector and were named as pG/1 and pG/10, respectively. Subsequently, they were introduced into the BmN and Bm-5 Bombyx mori cell lines by electro-transfection. A G418 (Geneticin) resistant Bombyx mori cell population has been selected out, following transfection.
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