Phosphatase on Chromosomes

Evidence that the endogenous histone H1 phosphatase in HeLa mitotic chromosomes is protein phosphatase 1, not protein phosphatase 2A.

Histone H1 is highly phosphorylated in mitotic HeLa cells, but is quickly dephosphorylated in vivo at the end of mitosis and in vitro following cell lysis. We show here that okadaic acid and microcystin-LR block the in vitro dephosphorylation of H1 and that they do so directly by inhibiting the histone H1 phosphatase rather than by some indirect mechanism. The concentrations of microcystin and ...

Another passenger on chromosomes

A synaptic scaffold quiets T cells scaffolding protein at neuronal synapses has found its way to another kind of synapse—the immune synapse, which forms at the interface between antigen presenting cells and T cells. As shown by Xavier et al. on page 173, this multi-domain protein, called Dlg1, tempers the activity of both types of synapses. On the T cell side of the immune syn-apse, activated T...

Eyes on chromosomes.

zeste protein on polytene chromosomes

Between PREs on Different Chromosomes

Polycomb response elements (PREs) can establish a silenced state that affects the expression of genes over considerable distances. We have tested the ability of insulator or boundary elements to block the repression of the miniwhite gene by the Ubx PRE. The gypsy element and the scs element interposed between PRE and miniwhite gene protect it against silencing but the SCS' is only weakly effect...