Stress induction of Bm1 RNA in silkworm larvae: SINEs, an unusual class ofstress genes

This study surveys the induction of RNA polymerase III (Pol III)-directed e xpression of short interspersed element (SINE) transcripts by various stres ses in an animal model, silkworm larvae. Sublethal heat shock and exposure to several toxic compounds increase the level of Bm1 RNA, the silkworm SINE transcript, while also transiently increasing expression of a well-charact erized stress-induced transcript, Hsp70 messenger RNA (mRNA). In certain ca ses, the Bm1 RNA response coincides with that of Hsp70 mRNA, but more often Bm1 RNA responds later in recovery. Baculovirus infection and exposure to certain toxic compounds increase Bm1 RNA but not Hsp70 mRNA, showing that S INE induction is not necessarily coupled to transcription of this particula r heat shock gene. SINES behave as an additional class of stress-inducible genes in living animals but are unusual as stress genes because of their hi gh copy number, genomic dispersion, and Pol III-directed transcription.