Conspicuous accumulation of transcription elongation repressor hrp130/CA150 on the intron-rich Balbiani ring 3 gene.

Chromosomal puffs on the polytene chromosomes in the dipteran Chironomus tentans offer the possibility of comparing the appearance of RNA-binding proteins at different transcription sites. We raised a monoclonal antibody that recognized a 130 kDa protein, designated hrp130. Immunocytological analysis of isolated chromosomes showed that hrp130 is heavily accumulated in a specific puff, called Balbiani ring 3; only occasionally is hrp130 abundant in one or two additional puffs on other chromosomes.

A p50-like Y-box protein with a putative translational role becomes associated with pre-mRNA concomitant with transcription.

In vertebrates free messenger ribonucleoprotein (RNP) particles and polysomes contain an abundant Y-box protein called p50 (YB-1), which regulates translation, presumably by affecting the packaging of the RNA. Here, we have identified a p50-like protein in the dipteran Chironomus tentans and studied its relation with the biogenesis of mRNA in larval salivary glands. The salivary gland cells contain polytene chromosomes with the transcriptionally active regions blown up as puffs.

A novel protein localized to the fibrillar compartment of the nucleolus and to the brush border of a secretory cell.

We report the identification and molecular characterization of a novel abundant nucleolar protein of the dipteran Chironomus tentans. As shown by Western blot analysis, this protein is present in nuclear extracts in a phosphorylated form with a mobility corresponding to 100 kDa. Therefore, the protein has been termed Chironomus tentans p100, or p100 for short.