Dynamics
A major surprise was the recent discovery from photobleaching experiments that linker histones to be a far more dynamic component of chromatin than core histones, with FRAP studies yielding a t50 of about 1 minute in somatic nuclei.
It is difficult to understand how such a dynamic protein could be a structural component of chromatin, but it has been suggested that the steady-state equilibrium within the nucleus still strongly favors association between H1 and chromatin, meaning that despite its dynamics, the vast majority of H1 at any given timepoint is chromatin bound.
Cytoplasmic factors appear to be necessary for the dynamic exchange of histone H1 on chromatin, but these have yet to be specifically identified. H1 dynamics may be mediated to some degree by O-glycosylation and phosphorylation. O-glycosylation of H1 may promote chromatin condensation and compaction. Phosphorylation during interphase has been shown to decrease H1 affinity for chromatin and may promote chromatin decondensation and active transcription. However, during mitosis phosphorylation has been shown to increase the affinity of H1 for chromosomes and therefore promote mitotic chromosome condensation (see Mitotic Phosphorylation by CDK1).
Read more about this topic: Histone H1
Famous quotes containing the word dynamics:
“Anytime we react to behavior in our children that we dislike in ourselves, we need to proceed with extreme caution. The dynamics of everyday family life also have a way of repeating themselves.”
—Cathy Rindner Tempelsman (20th century)