Overexpression of Hp95 induces G1 phase arrest in confluent HeLa cells.
Xp95, a protein recently identified in Xenopus laevis, is potentially involved in progesterone-induced Xenopus oocyte maturation. In this study, we cloned a human homologue of Xp95, designated Hp95, and examined the effect of its overexpression on the growth properties of human malignant HeLa cells which have lost the contact inhibition of cell proliferation. We observed that although HeLa cells did not undergo G1 phase arrest at any stage after confluence, they were able to downregulate their G1 phase CDK activities in response to confluence. When Hp95 was overexpressed in HeLa cells by transfection with a constitutive or an inducible expression vector containing a full-length Hp95 transgene, HeLa cells became able to undergo G1 phase arrest and form a monolayer culture after confluence. However, the G1 phase CDK activities in these Hp95 overexpressing cells were not inhibited further as compared to control cells after confluence. These results indicate that the defects in HeLa cells that cause the loss of contact inhibition of cell proliferation are in components downstream of the G1 phase CDKs and that overexpression of Hp95 counteracts some of these defects.
Wu
Y
Y
Department of Experimental Therapeutics, The University of Texas, M. D. Anderson Cancer Center, Houston 77030, USA.
Pan
S
S
Che
S
S
He
G
G
Nelman-Gonzalez
M
M
Weil
M M
MM
Kuang
J
J
D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002455:Cell Division / Q000235:genetics; D003001:Cloning, Molecular; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport; D005434:Flow Cytometry; D016193:G1 Phase; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D019076:Transgenes / Q000235:genetics
D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C117020:PDCD6IP protein, human; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases