Two distinct factors bind to the rabbit uteroglobin TATA-box region and are required for efficient transcription.

Abstract

The rabbit uteroglobin gene is expressed in a variety of epithelial cell types like the lung Clara cells and the glandular and luminal epithelial cells of the endometrium. Expression in Clara cells is on a high constitutive level, whereas expression in the rabbit endometrium is under tight hormonal control. One important element of the rabbit uteroglobin gene mediating its efficient transcription in two epithelial cell lines from human endometrium (Ishikawa) and lung (NCI-H441) is its noncanonical TATA box (TACA). Here, we show that two factors (TATA core factor [TCF] and TATA palindrome factor [TPF]) different from the TATA-box binding protein bind to the DNA major groove at two adjacent sites within the uteroglobin TATA-box region and that one of them (TCF) is specifically expressed in cell lines derived from uteroglobin-expressing tissues. The binding sites for TCF and TPF, respectively, are both required for efficient transcription in Ishikawa and NCI-H441 cells. Mutation of the TACA box, which we show is a poor TATA box in functional terms, to a canonical TATA motif does not affect TCF and TPF binding. Therefore, we suggest that the function of the unusual cytosine could be to reduce rabbit uteroglobin expression in cells lacking TCF and that the interaction of TATA-box binding protein with the weak TACA site is facilitated in TCF-and TPF-positive cells.

Binding of YY1 to a Site Overlapping a Weak TATA Box Is Essential for Transcription from the Uteroglobin Promoter in Endometrial Cells

“…1B). But previous results had shown that the wild-type promoter with its TACA box is sevenfold less active in driving reporter gene expression in CV-1 cells than a single-point mutant converting the TACA box to a TATA box (27). A very similar result was obtained with the TACA box of the adenovirus type 2 (Ad2) EIIa late promoter (EIIaL) (21).…”

“…Likewise, the ability of this TACA box to mediate activation by modulatory transcription factors was reduced by a factor of 10. Similarly, it was shown that a uteroglobin mutant in which the wild-type TACA box was converted to a TATA box is sevenfold more active than the wild-type construct in driving reporter gene expression in CV-1 cells (27). But in contrast to the rabbit gene, the human (score of Ϫ1.36) and the mouse and rat (score of Ϫ1.50) uteroglobin genes have bona fide TATA boxes with matrix scores not much lower than that of one of the strongest TATA boxes known, the Ad2 major late promoter TATA box (score of Ϫ0.91).…”

“…Regions II and VI contain binding sites for Sp1 family transcription factors (17), and region VII contains an estrogen responsive element (ER) (52). Region I encompasses the noncanonical TATA-box region (TACA), which is recognized by the tissuespecific factor TCF and the ubiquitous factor TPF (27), which was identified in this study as YY1. (B) Comparison of the rabbit uteroglobin (UG) TACA box (56), the cognate human (63), mouse (54), and rat (18) TATA sequences, the TATA box of the Ad2 major late promoter (6), and the TACA box of the Ad2 EIIaL promoter (21) with the TATA consensus sequence, using the weight matrix description of Bucher (6).…”

“…Coinciding with this observation, the uteroglobin promoter drives efficient transcription of a reporter gene in Ishikawa cells but not in HeLa cells (35,55) or CV-1 cells (27). It was also shown that two factors different from TBP, TATA core factor (TCF) and TATA palindrome factor (TPF), bind to the DNA major groove at two adjacent sites within this TACA-box region (27). Binding of each of these factors is functionally important, but only TCF is specifically expressed in cell lines derived from uteroglobin-expressing tissues, whereas TPF is ubiquitous.…”

“…We suggest that because of the absence of a standard core element, the rabbit promoter is very weak in all tissues that are not equipped with a set of factors, including YY1, able to mediate efficient transcription initiation despite its weak TATA box. In this respect, it will be important to uncover the role of TCF, which binds adjacent to the YY1 site (27).…”