Studies on sex and tissue specific BKM binding protein in mouse

Abstract

Bkm sequences were identified by isopycnic density gradient centrifugation from newlinethe genomic DNA of the female Banded Krait. Southern blot and in situ hybridization newlinestudies suggested that these sequences preferentially localise to the heteromorphic(W) newlinechromosome in most species of snakes except the primitive species, wherein sex newlinechromosomes are not differentiated. Unlike other repetitive DNA, Bkm sequences are newlinehighly conserved. They have been detected from yeast to man but are absent in newlineprokaryotes. Molecular cloning and sequencing of these repeats from Drosophila; snakes newlineand mouse showed that the conserved component of these repeats is a tandem array of newlinetetranucleotide repeats of GATA. newlineIn mouse, Bkm sequences are localised on the quotYquot chromosome. Using these newlinerepeats Singh and Jones elegantly demonstrated that in the dominant mutation Sxr the newlineBkm rich region on the quotYquot chromosome is duplicated and transferred onto the X newlinechromosome during meiosis.XX mice with the additional Bkm rich region develop as newlinemales. These results suggested that the Bkm rich region on the quotYquot chromosome is newlinenecessary and sufficient for male sex determination in mouse. Similar studies in humans newlinealso suggest that Bkm sequences are present in the sex determining region of the human newlinequotYquot chromosome. newlineScreening of a male genomic library of mouse with uncloned Bkm led to the newlineidentification of a clone M34. Unlike the Bkm repeats, M34 is not associated with the newlinesex determining region. Southern and in situ hybridization studies suggest that this clone newlineis repetitive and is distributed all along the long arm of the mouse quotYquot chromosome. M34 newlinewhen digested with EcoRI and Hindlll releases, among others, a 1.2 kb fragment(p3) newlinewhich is positive for GATA repeats. Sequencing of this fragment revealed the presence newlineof 32 repeats of GATA in a predominantly AT rich sequence(67% AT). p3 also contains newlinevi newline-, newlinesequences which show similarities to SAR( scaffold associated regions) sequences.