Genome stability and transcription by RNA polymerase II : Temperature-sensitive mutants of the largest subunit of pol II showing genome instability

RNA polymerase II (pol II) is a multi-subunit enzyme responsible for the transcription of most genes in eukaryotes. If forms enormous complexes, or holoenzymes, that associates with other proteins involved in related functions like splicing, polyadenylation, and the repair of damage in DNA. In turn, several such holoenzymes are organized into even larger structures called transcription factories (Cook, 1999). At the heart of each individual polymerizing complex lies the catalytic subunit, RPB1 this is the largest subunit found in the core enzyme. Sister chromatid exchange (SCE) is as an indicator of mutagenicity and carcinogenicity. A temperature-sensitive (ts) mutant of the CHO-K1 line, tsTM4, exhibited abnormal induction of SCEs along with a decrease of DNA synthesis in the cells arrested in S phase at the non-permissive temperature. These ts defects of tsTM4 were complemented by the human genomic fragments containing the entire coding region of RPB1 gene, as well as green fluorescent protein (GFP) tagged human rpb1 cDNA

Identification of the female-determining region of the W chromosome in Bombyx mori

The W chromosome of the silkworm Bombyx mori is devoid of functional genes, except for the putative female-determining gene (Fem). To localize Fem, we investigated the presence of W-specific DNA markers on strains in which an autosomal fragment containing dominant marker genes was attached to the W chromosome. We produced new W-chromosomal fragments from the existing Zebra-W strain (T(W;3)Ze chromosome) by X-irradiation, and then carried out deletion mapping of these and sex-limited yellow cocoon strains (T(W;2)Y-Chu, -Abe and -Ban types) from different Japanese stock centers. Of 12 RAPD markers identified in the normal W chromosomes of most silkworm strains in Japan, the newly irradiated W(B-YL-YS)Ze chromosome contained three, the T(W;2)Y-Chu chromosome contained six, and the T(W;2)Y-Abe and -Ban chromosomes contained only one (W-Rikishi). To investigate the ability of the reduced W-chromosome translocation fragments to form heterochromatin bodies, which are found in nuclei of normal adult female sucking stomachs, we examined cells of the normal type p50 strain and the T(W;2)Y-Chu and -Abe strains. A single sex heterochromatin body was found in nuclei of p50 females, whereas we detected only small sex heterochromatin bodies in the T(W;2)Y-Chu strain and no sex heterochromatin body in the T(W;2)Y-Abe strain. Since adult females of all strains were normal and fertile, we conclude that only extremely limited region, containing the W-Rikishi RAPD sequence of the W chromosome, is required to determine femaleness. Based on a comparison of the normal W-chromosome and 7 translocation and W-deletion strains we present a map of Fem relative to the 12 W-specific RAPD markers