Moshkin, Y.M., Alekseyenko, A.A., Semeshin, V.F., Spierer, A., Spierer, P., Makarevich, G.F., Belyaeva, E.S., Zhimulev, I.F. (2001). The Bithorax complex of Drosophila melanogaster. Underreplication and morphology in polytene chromosomes.  Proc. Natl. Acad. Sci. U.S.A. 98(2): 570--574.

FBrf0134831

Research paper

The level of polyteny of the Drosophila salivary gland chromosomes was determined throughout the chromosome region 89E1-4, the locus of the Bithorax Complex. A zone of underreplication spans the 300 kb of DNA from the Ubx to Abd-B loci. From the centromere proximal end of the complex, a 70-kb-long gradual decrease of polytenization starts with the Ubx transcription unit and, after a floor corresponding to the abd-A locus, raises gradually back to the maximum over 70 kb in the region of the Abd-B transcription unit. In flies carrying the mutation Suppressor of DNA Underreplication [Su(UR)ES], the underreplication of the Bithorax Complex is fully suppressed. In the wild type, the Bithorax Complex forms a weak point featuring thinner bands separated by clefts or constrictions. In Su(UR)ES strain in contrast, the 89E1-4 band looks like a single solid band consisting of homogenous dense material. We speculate that the wild-type Su(UR)ES protein hampers DNA replication of silenced domains and leads to their underreplication in salivary gland polytene chromosomes.

PMC14628 (PMC) (EuropePMC)