A. Houben et al., DIFFERENCES OF HISTONE-H4 ACETYLATION AND REPLICATION TIMING BETWEEN A-CHROMOSOMES AND B-CHROMOSOMES OF BRACHYCOME-DICHROMOSOMATICA, Chromosome research, 5(4), 1997, pp. 233-237
Differences are demonstrated between A (transcriptionally active) and
B (transcriptionally inactive) chromosomes that are characterized by a
different level of histone H4 acetylation and a different timing of D
NA replication. These differences between the chromatin of A and B chr
omosomes were found after immunolabelling of chromsomes of Brachycome
Dichromosomatica with antibodies specific for different acetylated for
ms (lysine 5, 8, 12 and 16) of histone H4. In contrast to the A chromo
somes, which are labelled brightly in their entirety, the transcriptio
nally inactive B chromosomes are faintly labelled with antibodies agai
nst H4Ac5 and H4Ac8. No such difference between the chromosomes is fou
nd after immunostaining with the other antibodies H4Ac12 and H4Ac16. A
nalysis of DNA replication timing in root-tip meristems suggests that
B chromosomes are labelled late in S-phase compared with A chromosomes
. After C-banding the B chromosome appeared to have a similar amount o
f heterochromatin to the A chromosomes.