High impact information on barr

• One of them is identified as a homolog of the Drosophila Barren protein whose mutation shows a defect in chromosome segregation [1].
• We have isolated a Drosophila gene, barren (barr), required for sister-chromatid segregation in mitosis. barr encodes a novel protein that is present in proliferating cells and has homologs in yeast and human [2].
• Colocalization and biochemical experiments indicate that Barren associates with Topoisomerase II throughout mitosis and alters the activity of Topoisomerase II [2].
• Here we report that Cnd2 (ref. 6), a non-SMC subunit of fission yeast similar to Drosophila Barren and the budding yeast protein Brn1 (refs 8, 9), is required for both interphase and mitotic condensation [3].
• This is associated with a reduction in levels of the serine 10 phosphorylated form of histone H3 and a failure to recruit the Barren condensin protein onto chromosomes [4].

Biological context of barr

• Mutations in barren (barr) were originally shown to affect sister-chromatid separation during mitosis 16 of the Drosophila embryo, whereas condensation defects were not detected [5].
• Our analyses indicate that inactivation of barr leads to extensive chromosome condensation and disrupts chromatid segregation [5].
• Additionally, Barren/CAP-H-depleted cells show chromosome congression defects that do not appear to be due to abnormal kinetochore-microtubule interaction [6].
• To further examine the role of condensin I in chromosome structure and in particular in centromere organization, we depleted from S2 cells the Drosophila CAP-H homologue Barren, a subunit exclusively associated with condensin I [6].

Other interactions of barr

• Instead, the centromeric and pericentromeric heterochromatin of Barren/CAP-H-depleted chromosomes shows structural problems [6].

Analytical, diagnostic and therapeutic context of barr

• Immunofluorescence and in vivo analysis of Barren/CAP-H-depleted cells showed that mitotic chromosomes are able to condense but fail to resolve sister chromatids [6].

References