title: The leukemia associated nuclear corepressor ETO homologue genes MTG16 and MTGR1 are regulated differently in hematopoietic cells.
abstract: BACKGROUND
  MTG16, MTGR1 and ETO are nuclear transcriptional corepressors of the human ETO protein family. MTG16 is implicated in hematopoietic development and in controlling erythropoiesis/megakaryopoiesis. Furthermore, ETO homologue genes are 3'participants in leukemia fusions generated by chromosomal translocations responsible of hematopoietic dysregulation. We tried to identify structural and functional promoter elements of MTG16 and MTGR1 genes in order to find associations between their regulation and hematopoiesis.
  
  
  RESULTS
  5' deletion examinations and luciferase reporter gene studies indicated that a 492 bp sequence upstream of the transcription start site is essential for transcriptional activity by the MTG16 promoter. The TATA- and CCAAT-less promoter with a GC box close to the start site showed strong reporter activity when examined in erythroid/megakaryocytic cells. Mutation of an evolutionary conserved GATA -301 consensus binding site repressed promoter function. Furthermore, results from in vitro antibody-enhanced electrophoretic mobility shift assay and in vivo chromatin immunoprecipitation indicated binding of GATA-1 to the GATA -301 site. A role of GATA-1 was also supported by transfection of small interfering RNA, which diminished MTG16 expression. Furthermore, expression of the transcription factor HERP2, which represses GATA-1, produced strong inhibition of the MTG16 promoter reporter consistent with a role of GATA-1 in transcriptional activation. The TATA-less and CCAAT-less MTGR1 promoter retained most of the transcriptional activity within a -308 to -207 bp region with a GC-box-rich sequence containing multiple SP1 binding sites reminiscent of a housekeeping gene with constitutive expression. However, mutations of individual SP1 binding sites did not repress promoter function; multiple active SP1 binding sites may be required to safeguard constitutive MTGR1 transcriptional activity. The observed repression of MTG16/MTGR1 promoters by the leukemia associated AML1-ETO fusion gene may have a role in hematopoietic dysfunction of leukemia.
  
  
  CONCLUSIONS
  An evolutionary conserved GATA binding site is critical in transcriptional regulation of the MTG16 promoter. In contrast, the MTGR1 gene depends on a GC-box-rich sequence for transcriptional regulation and possible ubiquitous expression. Our results demonstrate that the ETO homologue promoters are regulated differently consistent with hematopoietic cell-type- specific expression and function.
authors.affiliation: Department of Hematology, C14, BMC, S-221 84, Lund, Sweden. Ram.Ajore@med.lu.se
authors.forename: Ram
authors.initials: R
authors.lastname: Ajore
authors.forename: Parveen
authors.initials: P
authors.lastname: Kumar
authors.forename: Rakesh Singh
authors.initials: RS
authors.lastname: Dhanda
authors.forename: Urban
authors.initials: U
authors.lastname: Gullberg
authors.forename: Inge
authors.initials: I
authors.lastname: Olsson
mesh_terms: D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D001665:Binding Sites; D002144:Callithrix; D045744:Cell Line, Tumor; D050676:Core Binding Factor Alpha 2 Subunit / Q000378:metabolism; D050980:GATA Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006071:Gorilla gorilla; D006801:Humans; D007938:Leukemia / Q000378:metabolism / Q000473:pathology; D008253:Macaca mulatta; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015514:Oncogene Proteins, Fusion / Q000378:metabolism; D002679:Pan troglodytes; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D000075142:RUNX1 Translocation Partner 1 Protein; D051381:Rats; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000378:metabolism; D016385:TATA Box / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020298:U937 Cells
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D050676:Core Binding Factor Alpha 2 Subunit; D050980:GATA Transcription Factors; D015514:Oncogene Proteins, Fusion; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D000075142:RUNX1 Translocation Partner 1 Protein; D012097:Repressor Proteins; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C107844:AML1-ETO fusion protein, human; C110408:CBFA2T2 myeloid-transforming gene-related protein; C115744:CBFA2T3 protein, human; C405693:HEY2 protein, human; C082222:RUNX1T1 protein, human