Fig. 8. Model for how reversible AKAP95-PKA interaction (mediated by RII
phosphorylation) controls chromatin structure during mitosis. During interphase, AKAP95 and PKA-RII localize to distinct compartments, separated by the nuclear envelope. At mitosis entry, AKAP95 associates with condensing chromatin. RII is phosphorylated by the CDK1-cyclin-B complex. RII phosphorylation turns on a molecular switch promoting RII anchoring to AKAP95 and maintenance of condensed chromosomes during mitosis. (Although anchoring of RII to AKAP95 has been demonstrated, anchoring of the catalytic subunit of PKA is only suggested.) Throughout mitosis, anchoring of phosphorylated RII to chromatin-bound AKAP95 is required to prevent PCD. At mitosis exit, dephosphorylation of RII by a threonine phosphatase induces RII dissociation from chromatin-bound AKAP95. This relieves inhibition of chromatin decondensation, allowing chromosome decondensation as the nuclear envelope reassembles.
