p21 as a transcriptional co-repressor of S-phase and mitotic control genes.
It has been previously described that p21 functions not only as a CDK inhibitor but also as a transcriptional co-repressor in some systems. To investigate the roles of p21 in transcriptional control, we studied the gene expression changes in two human cell systems. Using a human leukemia cell line (K562) with inducible p21 expression and human primary keratinocytes with adenoviral-mediated p21 expression, we carried out microarray-based gene expression profiling. We found that p21 rapidly and strongly repressed the mRNA levels of a number of genes involved in cell cycle and mitosis. One of the most strongly down-regulated genes was CCNE2 (cyclin E2 gene). Mutational analysis in K562 cells showed that the N-terminal region of p21 is required for repression of gene expression of CCNE2 and other genes. Chromatin immunoprecipitation assays indicated that p21 was bound to human CCNE2 and other p21-repressed genes gene in the vicinity of the transcription start site. Moreover, p21 repressed human CCNE2 promoter-luciferase constructs in K562 cells. Bioinformatic analysis revealed that the CDE motif is present in most of the promoters of the p21-regulated genes. Altogether, the results suggest that p21 exerts a repressive effect on a relevant number of genes controlling S phase and mitosis. Thus, p21 activity as inhibitor of cell cycle progression would be mediated not only by the inhibition of CDKs but also by the transcriptional down-regulation of key genes.
Departamento de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC-SODERCAN, Santander, Spain.
Nuria
N
Ferrándiz
Juan M
JM
Caraballo
Lucía
L
García-Gutierrez
Vikram
V
Devgan
Manuel
M
Rodriguez-Paredes
M Carmen
MC
Lafita
Gabriel
G
Bretones
Andrea
A
Quintanilla
M Jose
MJ
Muñoz-Alonso
Rosa
R
Blanco
Jose C
JC
Reyes
Neus
N
Agell
M Dolores
MD
Delgado
G Paolo
GP
Dotto
Javier
J
León
D002460:Cell Line; D016000:Cluster Analysis; D056970:Co-Repressor Proteins / Q000378:metabolism*; D019295:Computational Biology / Q000379:methods; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000737:chemistry / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D020014:K562 Cells; D015603:Keratinocytes / Q000378:metabolism; D008938:Mitosis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016196:S Phase / Q000235:genetics*; D014158:Transcription, Genetic
C503688:CCNE2 protein, human; D056970:Co-Repressor Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D051357:Cyclin-Dependent Kinase 2