Effect of naturally occurring E2F-4 alterations on transcriptional activation and proliferation in transfected cells.
E2F is a family of transcription factors implicated in the regulation of gene expression required for progression through the G(1)-S transition. We have previously detected tumor-specific mutations at a trinucleotide repeat coding sequence of E2F-4 gene in a subset of human sporadic colorectal cancers. The purpose of this study was to investigate the potential functional consequences of these E2F-4 mutations. We transfected NIH3T3 fibroblasts with expression constructs containing wild-type as well as mutant E2F-4 cDNA, and the effect of the E2F-4 mutations on proliferation was examined. Alteration in transactivation of the E2F consensus promoter sequence was also examined by transient cotransfection of a E2F-4 with a DP-2 construct into cultured human cells. Transfected cell clones overexpressing mutant E2F-4 grew more rapidly and showed higher proliferative activity by increased immunohistochemical staining for proliferating cell nuclear antigen (PCNA). All three mutant forms of E2F-4 showed elevated transactivation of the E2F consensus promoter sequence. Thus, expression of mutant E2F-4s confers a growth advantage in vivo, and this effect may be related to the acquisition of a neoplastic phenotype.
Takashima
H
H
Department of Gastroenterological Surgery and Surgical Oncology, Okayama University Graduate School of Medicine, Okayama, Japan.
Matsumoto
Y
Y
Matsubara
N
N
Shirakawa
Y
Y
Kawashima
R
R
Tanino
M
M
Ito
S
S
Isozaki
H
H
Ouchida
M
M
Meltzer
S J
SJ
Shimizu
K
K
Tanaka
N
N
D016475:3T3 Cells; D000818:Animals; D002455:Cell Division / Q000235:genetics; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics*; D050704:E2F4 Transcription Factor; D005434:Flow Cytometry; D016193:G1 Phase / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008819:Mice, Nude; D016296:Mutagenesis / Q000502:physiology; D016196:S Phase / Q000235:genetics; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics*; D015533:Transcriptional Activation / Q000235:genetics*; D014162:Transfection; D019737:Transplants
D004268:DNA-Binding Proteins; D050704:E2F4 Transcription Factor; D014157:Transcription Factors