Transcription of the MAT2A gene, coding for methionine adenosyltransferase, is up-regulated by E2F and Sp1 at a chromatin level during proliferation of liver cells.
Methionine adenosyltransferase (MAT) is an essential enzyme because it catalyzes the formation of S-adenosylmethionine, the main methyl donor. Two MAT-encoding genes (MAT1A, MAT2A) are found in mammals. The latter is expressed in proliferating liver, dedifferentiation and cancer, whereas MAT1A is expressed in adult quiescent hepatocytes. Here, we report studies on the molecular mechanisms controlling the induction of MAT2A in regenerating rat liver and in proliferating hepatocytes. The MAT2A is up-regulated at two discrete moments during liver regeneration, as confirmed by RNApol-ChIP analysis. The first one coincides with hepatocyte priming (i.e. G0-G1 transition), while the second one takes place at the G1-S interface. Electrophoretic mobility shift assays showed that a putative E2F sequence present in MAT2A promoter binds this factor and ChIP assays confirmed that E2F1, E2F3 and E2F4, as well as the pocket protein p130, are bound to the promoter in quiescent liver. MAT2A activation is accompanied by changes in the binding of histone-modifying enzymes to the promoter. Interestingly, p130 is not displaced from MAT2A promoter during hepatocyte priming, but it is in the late expression of the gene at the G1-S transition. Finally, the transcription factor Sp1 seems to play a decisive role in MAT2A induction, as it binds the promoter when the gene is being actively transcribed. In summary, the present work shows that the molecular mechanism of MAT2A expression is different during G0-G1 or G1-S transition and this may be related to the distinct requirements of S-adenosylmethionine during liver regeneration.
Rodríguez
José L
JL
Department of Biochemistry and Molecular Biology, University of Valencia, Spain.
Boukaba
Abdelhalim
A
Sandoval
Juan
J
Georgieva
Elena I
EI
Latasa
M Ujue
MU
García-Trevijano
Elena R
ER
Serviddio
Gaetano
G
Nakamura
Toshikazu
T
Avila
Matías A
MA
Sastre
Juan
J
Torres
Luis
L
Mato
José M
JM
López-Rodas
Gerardo
G
D000818:Animals; D001483:Base Sequence; D049109:Cell Proliferation; D002478:Cells, Cultured; D002843:Chromatin / Q000235:genetics / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D050684:E2F Transcription Factors / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D016193:G1 Phase / Q000235:genetics; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D008115:Liver Regeneration / Q000235:genetics; D008297:Male; D008716:Methionine Adenosyltransferase / Q000235:genetics*; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D016196:S Phase / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D014158:Transcription, Genetic; D015854:Up-Regulation
D002843:Chromatin; D050684:E2F Transcription Factors; D009841:Oligonucleotides; D016329:Sp1 Transcription Factor; C512846:Mat2a protein, rat; D008716:Methionine Adenosyltransferase