DNA bound to octameric histones can be further compacted by
linker histones such as histone H1. In work that was published
in the JCB, Heald and colleagues showed that H1 function is
necessary for mitosis in Xenopus egg extracts. In its absence,
chromosomes become tangled up and do not segregate properly.
Heald presented new work comparing the function of embryonic and
somatic isoforms of histone H1. They examined whether the
different isoforms can substitute for each other and the effects
of this substitution on chromosome architecture. Surprisingly,
isoforms have different properties and regulation despite
extensive homology between them. By analyzing the proteins that
interact specifically with one isoform vs. another, they are
starting to get a handle on how these linker histones
differentially control chromosome structure. Heald then moved on
to talk about her lab’s work on determinants of organelle size,
namely the nucleus. Previously in The JCB, Heald and colleagues
observed that spindle size was affec