The Serotonin 1a Receptor Gene Contains a TATA-less Promoter that Responds to MAZ and Sp1

Abstract

The structure and function of the 5'-flanking region of the mouse and human serotonin 1a receptor gene have been analyzed by RNA 5' end mapping, DNA-protein interaction, and transient expression assays. A large number of mRNA 5' termini, detected by mapping 5' ends from mouse brain RNA, were found dispersed over a region of about 700 base pairs flanking the receptor coding sequence. Consistent with the apparently heterogeneous pattern of transcription initiation, the flanking DNA sequence lacked typical TATA box elements and was rich in guanine and cytosine. The mouse and human 5'-flanking sequences were 63% homologus and similarly organized. A guanine-cytosine-rich DNA sequence motif related to the sequence 5'-GGGG(C/A)GGGG-3' was repeated within the 5'-flanking region and located at or near several mRNA 5' ends. This DNA sequence motif bound to proteins in a crude HeLa cell nuclear extract. A cDNA encoding a protein that interacts with this sequence was cloned and found to be the MAZ (Pur-1, Zif87) protein. The interaction between MAZ and the receptor gene 5'-flanking region proximal to the protein coding sequence was examined by DNase I footprinting, and four sites of MAZ interaction were identified. Three of the four MAZ binding sites also were shown to interact with transcription factor Sp1. Overproduction of MAZ or Sp1 in transient transfection assays increased expression directed by the human 5'-flanking sequence, although MAZ was substantially more effective. This result suggests that MAZ and Sp1 both participate in regulating expression from the serotonin 1a receptor gene promoter, and it raises the possibility that MAZ may act at a variety of promoters through the guanosine-cytosine-rich sequences generally thought to serve as binding sites for the Sp1 family of transcription factors. Analysis of one of the guanosine-cytosine-rich DNA sequences also revealed that it can serve as a transcription initiator sequence in vitro. This initiator sequence differs from previously characterized initiators and may represent a new class of this transcriptional control sequence.

p53 promotes adenoviral replication and increases late viral gene expression

“…Cells were fixed and stained for p53 and DBP expression, then visualized by immunofluorescence microscopy. that E1a alone gave low expression as reported previously (Parks and Shenk, 1997), but that E1a in conjunction with p53 caused a dose-dependent increase in MLP CAT activity, which was up to 300-fold higher than E1a alone. The level of p53 enhancement varied between cell lines, with HeLa giving the greatest enhancement of 300-fold at 15 pg of CMVhp53 per dish of 2 Â 10 5 cells.…”

“…It could be that p53 helps to stabilize an interaction between E1a and essential transcription factors on the MLP, thereby enhancing transcription. The interaction with Sp1 would have to be a strong candidate, given its marked ability to cooperate with E1a (Parks and Shenk, 1997). In this respect, it is interesting to note that we have found transfection of exogenous E1a into dl1520-infected K1scx cells increases virus yield approximately 10-fold, with little effect on wtAd5 (results not shown).…”

“…The possibility exists that p53 could act as a chaperone or intermediary, bringing together components of the transcription machinery at the required DNA sites. The MLP contains binding sites for several transcription factors, including the CCAATbox binding factor, the TATA-box binding protein (reviewed in and the transcription factor Sp1 (Parks and Shenk, 1997), all of which have been reported to interact with both p53 (reviewed in Prives and Hall, 1999) and E1a (reviewed in . It could be that p53 helps to stabilize an interaction between E1a and essential transcription factors on the MLP, thereby enhancing transcription.…”

MAZ, a Myc-associated zinc finger protein, is essential for the ME1a1-mediated expression of the c-myc gene during neuroectodermal differentiation of P19 cells

“…Recently, we reported isolation of a cDNA clone for a member of the family of MAZ proteins in human islet cells that had a similar DNA-binding speci®city (Tsutsui et al, 1996). A MAZ plays a role in the control of the initiation of transcription of genes for CD4 (Duncan et al, 1995) and serotonin (Parks and Shenk, 1996) and in the termination of transcription between closely spaced human genes for complement (Ash®eld et al, 1994) and also between the introns of the mouse gene for IgM-D (Ash®eld et al, 1994). Therefore, MAZ appears to be a transcriptional factor with a dual role in the initiation and termination of transcription.…”

Molecular cloning and characterization of the 5′ region of the mouse trkA proto-oncogene

“…This DNA segment contains potential binding sites for several factors, including Sp1, MAZ, GCF and AP-2. Sp1 and MAZ are general transcription activators that have been proposed as important regulators of TATA-less promoters (Parks and Shenk, 1996), whereas GCF acts as a repressor for GC-rich promoters (Kageyama and Pastan, 1989); in the other hand, AP-2 is a speci®c transcriptional activator present in neural crest-derived lineages (Mitchell et al, 1991). Thus, both positive and negative transcription factors as well as general and speci®c ones, can potentially interact with the cisregulatory element at the trkA promoter in order to regulate its expression (Figure 5a).…”