Cloning of GT box-binding proteins: a novel Sp1 multigene family regulating T-cell receptor gene expression.

Abstract

Analysis of a T-cell antigen receptor (TCR) a promoter from a variable gene segment (V) revealed a critical GT box element which is also found in upstream regions of several Va genes, TCR enhancer, and regulatory elements of other genes. This element is necessary for TCR gene expression and binds several proteins. These GT box-binding proteins were identified as members of a novel Spl multigene family. Two regions (for reviews, see references 5 and 27). The process of V-D-J gene rearrangements is developmentally and tissue specifically regulated. The TCR a and 8 genes are particularly interesting because the 8 locus is located within the TCR a-gene segments. In T cells committed to the a,3 lineage, the a-specific V-gene segments are rearranged to the a locus, whereas in cells committed to the -yb lineage, the b-specific V-gene segments are rearranged to their respective D/Jb gene segments. Some V gene segments, however, can rearrange to either the a or 8 locus (these gene segments are also called Va).Studies using transgenic mice and cell lines suggest that specific gene segment transcription correlates with differential accessibility of each locus to the recombinase during development (8, 7). Production of sterile transcripts from unrearranged gene segments, in particular, has been found to precede gene rearrangement. It is hypothesized that sterile transcription is either the cause or the consequence of differential opening of chromatin structure and hence accessibility of the gene segment to the recombination enzymes (references 7 and 28 and references therein). Since each of the V-gene segments contains its own promoter, it is possible that the specificity of sterile transcription from these V promoters could contribute to differential accessibility to recombinases during T-cell development, which could result in specific gene segment usage in aot and/or 9y T cells (35). * Corresponding author.Therefore, the study of TCR a promoters can serve the dual purpose of analyzing TCR gene expression as well as regulation of rearrangement.We have focused on the well-characterized Vall.1 gene segment, which is the gene segment predominantly used in T-cell response to pigeon cytochrome c (9, 38). We have analyzed the critical elements for the Vall.1 promoter and found one element which we called the GT box. This GT box is also present in most other available Va upstream sequences (presumably promoters) as well as in the TCR ax enhancer. Homologous regulatory elements (AC boxes) were previously defined in the ,-globin enhancers, promoters, and locus-controlling region (LCR) as well as in the bovine papillomavirus (BPV) promoters and simian virus (SV40) enhancer. This novel element for T-cell gene expression was shown to bind ubiquitously expressed proteins, one of which was identified as the transcription factor Spl (18). Although Spl is one of the earliest-characterized transcription factors which also binds to a consensus GC box sequence, we have made the assumption that additional GT box-binding proteins contain se...

Differences in DNA‐binding efficiency of Sp1 to aldolase and pyruvate kinase promoter correlate with altered redox states in resting and proliferating rat thymocytes

“…These data indicate that the upper complex contains Spl, the lower complex may include an Spl-related protein. The formation of two major complexes with the Spl-binding site was also reported by others [20,21]. From the band intensities it appears that the nuclear extract from proliferating thymocytes yields more intense Spl bands (Fig.…”

Overlapping Sp1 and AP2 binding sites in a promoter element of the lens-specific MIP gene

“…We found that the human MIP gene sequence -253/+42 contains an active promoter in cultured lens cells but is inactive in non-lens cells (17). In the present study we have characterized a cis regulatory element required for MIP gene (18,19), is present in lens nuclear extracts and also interacts with this Sp1 binding site. Even though Sp1 is a ubiquitous factor, it regulates tissue-specific expression of a variety of genes (20)(21)(22)(23)(24)(25).…”

“…However, as other members of the Sp family also interact with this motif (18,19) it was important to determine which member was involved in interaction with the CT box present at positions -55/-49 of the functional MIP promoter. When the oligonucleotide -67/-38 was incubated with mouse lens nuclear extract two retarded bands, C1 and C2, were observed (Fig.…”

“…Sp1 was a monoclonal antibody corresponding to amino acids CKDSEGRGSG DPGKKKQHI (19), Sp2 is a polyclonal antibody to amino acids KGTRSNANIQYQAVPQIQAS (18,19), Sp3 is a polyclonal antibody to amino acids DILTNTEIPLQLVTVSGNET (18,19) and Sp4 is a polyclonal antibody to amino acids VTVAAISQDSNPATPNVSTN (18).…”

The transcriptional activator Sp1, a novel autoantigen

“…Proliferating cell nuclear antigen is an example of a protein originally identified as a human autoantigen that was later shown to have counterparts in many eukaryotic cells of different species (24). Anti-Spl autoimmune sera may be useful to search for Spl analogs in other species and to identify other human Spl-like proteins (27)(28)(29)(30). Some autoantibodies also recognize epitopes that are functionally important (24).…”