Modulation of nuclear matrix protein phosphorylation by histones: Possibleinvolvement of NM-Associated protein kinase CK2 activity

Nuclear matrix (NM), a proteinaceous network of filaments, dictates nuclear morphology and the structure/function of DNA. Phosphorylation of NM protei ns is a potential signal for regulating matrix functions. Histones also ar e intimately involved in DNA structure and transcription. Here, we report t hat various histones enhanced P-32 incorporation into certain NM proteins. Modulation of NM protein phosphorylation by histones is mediated through re gulation of protein kinase CK2, a messenger-independent serine/threonine ki nase, which is significantly associated with the NM. The stimulatory effect of histones was mitigated by prior incubation of histones with DNA in the reaction. Phosphorylation of NM proteins was extensively reduced when an ex cess of the CK2-specific peptide substrate was included in the phosphorylat ion reaction as a competitor. Also, enhancement in the NM-associated CK2 ac tivity by histones was blocked by inhibitors of CK2. Histone H1 effect appe ared to be mediated mainly by charge effect since a stretch of polylysine i nduced a similar effect. Various histones also differentially affected the autophosphorylation of NM-associated CK2 subunits. This may contribute to t he observed effects of histones on the NM, resulting in an enhancement and differential pattern of NM protein phosphorylation. Such a regional modific ation of NM protein phosphorylation might influence the nuclear functions t hat require histone displacement, namely, replication and transcription. J. Cell. Biochem. 72.242-250, 1999. Published 1999 Wiley-Liss, Inc.