Extracellular signal-regulated kinase 1/2 activity is not required in mammalian cells during late G2 for timely entry into or exit from mitosis.

Extracellular signal-regulated kinase (ERK)1/2 activity is reported to be required in mammalian cells for timely entry into and exit from mitosis (i.e., the G2-mitosis [G2/M] and metaphase-anaphase [M/A] transitions).

The p38-mediated stress-activated checkpoint. A rapid response system for delaying progression through antephase and entry into mitosis.

Cells have evolved a number of control pathways that delay or prevent them from entering mitosis under conditions that can compromise genome integrity. One recently appreciated and versatile control pathway involves the p38 stress activated protein kinase. During late G2 p38 is rapidly activated by diverse stresses (topoisomerase II (topo II)) and histone deacetylase inhibitors, osmotic shock, microtubule disassembly, UV light, etc) via a number of different pathways.

Topoisomerase II and histone deacetylase inhibitors delay the G2/M transition by triggering the p38 MAPK checkpoint pathway.

When early prophase PtK(1) or Indian muntjac cells are exposed to topoisomerase II (topo II) inhibitors that induce little if any DNA damage, they are delayed from entering mitosis. We show that this delay is overridden by inhibiting the p38, but not the ATM, kinase. Treating early prophase cells with hyperosmotic medium or a histone deacetylase inhibitor similarly delays entry into mitosis, and this delay can also be prevented by inhibiting p38.