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Differential occurrence of CSF‐like activity and transforming activity of Mos during the cell cycle in fibroblasts.
Author(s) -
Okazaki K.,
Nishizawa M.,
Furuno N.,
Yasuda H.,
Sagata N.
Publication year - 1992
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1992.tb05309.x
Subject(s) - okazaki fragments , molecular genetics , cell division , biology , genetics , gene , cell , dna replication , eukaryotic dna replication
The Xenopus c‐mos proto‐oncogene product, Mosxe, possesses cytostatic factor (CSF) activity to arrest maturing oocytes in metaphase II and has weak transforming activity in mouse NIH3T3 cells. We show that Mosxe mutants bearing ‘stabilizing’ penultimate N‐terminal amino acids are strongly transforming and can retard progression through the G2‐M phases in Mosxe‐transformed cells, probably via their CSF activity. On the other hand, a cyclin‐Mosxe fusion protein, which undergoes abrupt degradation at the end of mitosis and is restored to its normal levels only after the G1 phase, transforms cells much less efficiently than a mutated cyclin‐Mosxe fusion protein that is stable during M‐G1 transition. Moreover, in low‐serum medium, cells transformed by the unstable cyclin‐Mosxe require a long period to enter the S phase, in contrast with the rapid entry into the S phase of cells transformed by the stable cyclin‐Mosxe. These results provide strong evidence that unlike the physiological CSF activity, the transforming activity of Mos is exerted in the G1 phase of the cell cycle.