Cloning and functional characterization of the 5'-flanking region of human methionine adenosyltransferase 1A gene.
Methionine adenosyltransferase (MAT) is an essential cellular enzyme which catalyses the formation of S-adenosylmethionine, the principal methyl donor and precursor for polyamines. In mammals, two different genes, MAT1A and MAT2A, encode for liver-specific and non-liver-specific MAT respectively. We previously described a switch in the MAT expression from MAT1A to MAT2A in human liver cancer, which offered the cancerous cell a growth advantage. Loss of MAT1A expression was due to lack of gene transcription. To study regulation of the MAT1A gene, we have cloned and characterized a 1.9 kb 5'-flanking region of the human MAT1A gene. One transcriptional start site, located 25 nt downstream from a consensus TATA box, was identified by primer extension and RNase protection assays. The promoter contains several consensus binding sites for CAAT enhancer binding protein (C/EBP) and hepatocyte-enriched nuclear factor (HNF), transcriptional factors important in liver-specific gene expression. The human MAT1A promoter was able to efficiently drive luciferase expression in Chang cells, a human liver cell line, but not in HeLa cells. Sequential deletion analysis of the promoter revealed two DNA regions upstream of the translational start site, -705 to -839 bp and -1111 to -1483 bp, which are involved in positive and negative gene regulation, respectively. Specific protein binding to these regions was confirmed by electrophoretic-mobility-shift and DNase I footprinting assays. Similar to the situation with the rat MAT1A, glucocorticoid treatment also increased human MAT1A expression and promoter activity in a dose- and time-dependent manner.
Zeng
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Z
Division of Gastroenterology and Liver Diseases, Department of Medicine, USC Liver Disease Research Center, USC School of Medicine, 2011 Zonal Avenue, Los Angeles, CA 90033, USA.
Huang
Z Z
ZZ
Chen
C
C
Yang
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H
Mao
Z
Z
Lu
S C
SC
D020121:5' Untranslated Regions / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D006801:Humans; D008716:Methionine Adenosyltransferase / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D051381:Rats; D017421:Sequence Analysis
D020121:5' Untranslated Regions; D008716:Methionine Adenosyltransferase