Banded krait minor-satellite (Bkm)-associated Y chromosome-specific repetitive DNA in mouse

The mouse Y chromosome remains highly condensed in all somatic tissues but decondenses extensively in testis. We have isolated a mouse Y chromosome-specific repeat M34 (11.5 kb) and shown that this is distributed along the Y chromosome except the sex-determining region (the Y short arm) in which GATA repeats are predominantly concentrated. It has 32 copies of GATA repeats in a 2.7 kb fragment. About 200-300 copies of M34 on the Y chromosome are interspersed among other sequences. A 1.2 kb fragment (p3) of M34, containing GATA repeats, also has scaffold attachment region (SAR) motifs which bind to nuclear matrices. A strong affinity of histone H1 to SAR motifs is implicated in maintaining the condensed state of the Y chromosome in somatic tissues. The probable significance of molecular organization of the Y chromosome is discussed.