Chromatin immunoselection defines a TAL-1 target gene

Abstract

S.Cohen-Kaminsky and L.Maouche-Chrétien contributed equally to this workDespite the major functions of the basic helix-loophelix transcription factor TAL-1 in hematopoiesis and T-cell leukemogenesis, no TAL-1 target gene has been identified. Using immunoprecipitation of genomic fragments bound to TAL-1 in the chromatin of murine erythro-leukemia (MEL) cells, we found that 10% of the immunoselected fragments contained a CAGATG or a CAGGTG E-box, followed by a GATA site. We studied one of these fragments containing two E-boxes, CAGATG and CAGGTC, followed by a GATA motif, and showed that TAL-1 binds to the CAGGTG E-box with an affinity modulated by the CAGATG or the GATA site, and that the CAGGTG-GATA motif exhibits positive transcriptional activity in MEL but not in HeLa cells. This immunoselected sequence is located within an intron of a new gene co-expressed with TAL-1 in endothelial and erythroid cells, but not expressed in fibroblasts or adult liver where no TAL-1 mRNA was detected. Finally, in vitro differentiation of embryonic stem cells towards the erythro/megakaryocytic pathways showed that the TAL-1 target gene expression followed TAL-1 and GATA-1 expression. These results establish that TAL-1 is likely to activate its target genes through a complex that binds an E-box-GATA motif and define the first gene regulated by TAL-1.

The Mouse Fetoprotein Transcription Factor (FTF) Gene Promoter Is Regulated by Three GATA Elements with Tandem E Box and Nkx Motifs, and FTF in Turn Activates the Hnf3β, Hnf4α, and Hnf1α Gene Promoters

“…Furthermore, a second FTF promoter E box element is present two nucleotides downstream from the first one and appears to down-regulate FTF promoter activity (Fig. 3B, lane 8); this strikingly reproduces a variant hematopoietic GATA/E box motif in which the second E box serves to attenuate the adjacent GATA1-Tal1 multiprotein activatory complex (35). Differential mFTF promoter activity between tissues or developmental stages might then finely respond to changing combinations of activatory or repressor components forming the GATA/E boxes complex.…”

Molecular Hallmarks of Endogenous Chromatin Complexes Containing Master Regulators of Hematopoiesis

“…In gel-shift assays using MEL cell nuclear extracts, GATA-1, the E-proteins Scl/ TAL1 and E2A, and their interacting proteins Lmo2 and Ldb1 assemble a complex on oligonucleotides containing E-box and WGATAR or GATA motifs (83,84,89). Sequences containing both E-box and WGATAR motifs, but considerably larger than the 40-bp composite elements that we analyzed, activate reporter genes in transiently transfected MEL cells (2,14,89) and in erythroid cells in vivo (83). The 1.7-kb P4.2 promoter, which contains two E-box-WGATAR composite FIG.…”

Differences in the chromatin structure and cis-element organization of the human and mouse GATA1 loci: implications for cis-element identification

“…42 Others similarly demonstrated in vitro complex assembly on variations of the original GATA-Ebox element or on GATA sites alone, at regulatory sequences of other genes. [66][67][68] Finally, recent data suggest that all the components of this complex function with the ubiquitous transcription factor Sp1 to regulate expression of the red cell-specific glycophorin A gene. 69 In the specific case of transcriptional control of GATA1, SCL, LMO2, and GATA2 all act upstream of GATA1 (reviewed in Orkin 15 ) and are candidate GATA1 regulators.…”