Premium
Cell cycle function of a Medicago sativa A2‐type cyclin interacting with a PSTAIRE‐type cyclin‐dependent kinase and a retinoblastoma protein
Author(s) -
Roudier François,
Fedorova Elena,
Györgyey Janos,
Feher Attila,
Brown Spencer,
Kondorosi Adam,
Kondorosi Eva
Publication year - 2000
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.2000.00794.x
Subject(s) - biology , cell cycle , cyclin a , cyclin , cyclin a2 , microbiology and biotechnology , mitosis , retinoblastoma protein , cyclin b , cyclin dependent kinase 1 , cyclin dependent kinase , cyclin d , cyclin e , cyclin b1 , genetics , cell
Summary In plants multiple A‐type cyclins with distinct expression patterns have been isolated and classified into three subgroups (A1–A3), while in animal somatic cells a single type of cyclin A is required for cell‐cycle regulation from the S to M phases. We studied the function of an A2‐type cyclin from Medicago sativa ( Medsa; cycA2 ) which, in contrast to animal and most plant A‐type cyclins, was expressed in all phases of the cell cycle. Using synchronized alfalfa cell cultures and anti‐Medsa;CycA2 polyclonal antibodies, we showed that while the mRNA level increased steadily from the late G1 to the G2‐M phase, the protein level after a rapid increase in S‐phase reached a plateau during the G2 phase. In the yeast two‐hybrid system, the Medsa;CycA2 protein interacted with the PSTAIRE‐motif‐containing cyclin‐dependent kinase Cdc2MsA and with the maize retinoblastoma protein. Unexpectedly, the CycA2‐associated kinase activity was biphasic: a first activity peak occurred in the S phase while the major one occurred during the G2/M transition, with no apparent dependence upon the actual levels of the Medsa;CycA2 and Cdc2MsA proteins. Immunohistological localization of the cyclin A2 protein by immunofluorescence and immunogold labelling revealed the presence of Medsa;CycA2 in the nucleus of the interphase and prophase cells, while it was undetectable thereafter during mitosis. Together these data suggest that Medsa;CycA2 plays a role both in the S phase and at the G2/M transition.