A PSTAIRE CDK-like protein localizes in nuclei and cytoplasm of Physarum polycephalum and functions in the mitosis

Abstract

CDKs play key roles in controlling cell cycle progression in all eukaryotes. In plants, multiple CDKs are present, among which the best characterized CDKs are PSTAIRE CDKs. In this study, we carried out Western blot, immunoelectron microscopy and antibody treatment with an anti-PSTAIRE monoclonal antibody to explore the subcellular localization and functions of PSTAIRE CDKs in Physarum polycephalum. The results of Western blot and immunoelectron microscopy showed that in P. polycephalum, a PSTAIRE CDK-like protein was 34 kD in molecular weight and located in both nuclei and cytoplasm. In nuclei, the protein was mainly associated with chromosomes and nucleoli. The expression of the PSTAIRE CDK-like protein in both the plasmodia and nuclei showed little fluctuation through the whole cell cycle. When treated with an anti-PSTAIRE monoclonal antibody at early S phase, the cells were arrested in S phase, and the mitotic onset of P. polycephalum was blocked for about 1 h when treated at early G2 phase. Our data indicated that the PSTAIRE CDK-like protein has a direct bearing on the mitosis.

Genome-wide identification, evolutionary and expression analysis of the cyclin-dependent kinase gene family in peanut

“…A glycine-rich inhibitory element (G-loop) and a cyclin binding evolutionary conserved 16 amino acid sequence (EGVPSTAI-REISLLKE) motif called PSTAIRE remain in the N-lobe (PSTAIRE motif in case of CDKA). The C-lobe contains an extended activation segment comprising a phosphorylation-sensitive T-loop in between both DFG and APE motif required for accelerating enzymatic activity by unlocking the catalytic pocket [ 3 , 4 ]. Although substrate binding and stabilization of the interaction between kinase-substrate are stringently operated by C-lobe, the kinase activity can be inhibited by phosphorylation of threonine residues at G-loop in the N-lobe [ 5 ].…”