Histone H2A insufficiency causes chromosomal segregation defects due to anaphase chromosome bridge formation at rDNA repeats in fission yeast

Abstract

The nucleosome, composed of DNA and a histone core, is the basic structural unit of chromatin. The fission yeast Schizosaccharomyces pombe has two genes of histone H2A, hta 1 + and hta 2 + ; these genes encode two protein species of histone H2A (H2Aα and H2Aβ, respectively), which differ in three amino acid residues, and only hta2 + is upregulated during meiosis. However, it is unknown whether S. pombe H2Aα and H2Aβ have functional differences. Therefore, in this study, we examined the possible functional differences between H2Aα and H2Aβ during meiosis in S. pombe . We found that deletion of hta2 + , but not hta1 + , causes defects in chromosome segregation and spore formation during meiosis. Meiotic defects in hta2 + deletion cells were rescued by expressing additional copies of hta1 + or by expressing hta1 + from the hta2 promoter. This indicated that the defects were caused by insufficient amounts of histone H2A, and not by the amino acid residue differences between H2Aα and H2Aβ. Microscopic observation attributed the chromosome segregation defects to anaphase bridge formation in a chromosomal region at the repeats of ribosomal RNA genes (rDNA repeats). These results suggest that histone H2A insufficiency affects the chromatin structures of rDNA repeats, leading to chromosome missegregation in S. pombe .

A visual atlas of meiotic protein dynamics in living fission yeast

“…Our observations of H3 histone (Hht1-mRFP) dynamics generally agree with those of other live-cell studies (Ding et al, 2006; Escorcia and Forsburg, 2017; Fennell et al, 2015; Klutstein et al, 2015; Tomita et al, 2013; Yamamoto et al, 2019; Yang et al, 2015). The timing from nuclear fusion to meiosis II takes approximately 4 ½ hours, which is in line with previous reports (Ding et al, 2006; Moiseeva et al, 2017; Tomita et al, 2013).…”

A visual atlas of meiotic protein dynamics in living fission yeast

“…Our observations of H3 histone (Hht1-mRFP) dynamics generally agree with those of other live-cell studies [19,23,[28][29][30][31][32]. The timing from nuclear fusion to MII takes approximately 4½ hours, which is in line with previous reports [23,28,33].…”

Age related changes of rib cortical bone matrix and the application to forensic age-at-death estimation

“…However, this is related to a number of modifications in crystallite size and overall crystallinity 40 – 43 . This is in part due to the effect of impaired remodelling with age, osteocalcin 43 , 44 , and changes in hydroxyapatite composition, such as the reduction in a-axis length with the increase in carbonate substitution as well as the increase in overall crystal size 41 , 45 – 47 . In the present study, there is a robust increase in mineral content (R 2 = 0.41 and p < 0.001) accompanied by the increase in carbonate substitution, a trend which has recently been confirmed by Pedrosa et al 29 Results for the present study support previous findings showing that mineralisation increases until maturity is reached.…”