Transcriptional regulation of a pair-rule stripe in Drosophila.

Abstract

The periodic, seven-stripe pattern of the primary pair-rule gene even-skipped (eve) is initiated by crude, overlapping gradients of maternal and gap gene proteins in the early Drosophila embryo. Previous genetic studies suggest that one of the stripes, stripe 2, is initiated by the maternal morphogen bicoid (bcd} and the gap protein hunchback (hb), while the borders of the stripe are formed by selective repression, involving the gap protein giant (gt) in anterior regions and the Kriippel (Kr) protein in posterior regions. Here, we present several lines of evidence that are consistent with this model for stripe 2 expression, including in vitro DNA-binding experiments and transient cotransfection assays in cultured cells. These experiments suggest that repression involves a competition or short-range quenching mechanism, whereby the binding of gt and Kr interferes with the binding or activity of bcd and hb activators at overlapping or neighboring sites within the eve stripe 2 promoter element. Such short-range repression could reflect a general property of promoters composed of multiple, but autonomous regulatory elements.

Investigating giant (Gt) repression in the formation of partially overlapping pair‐rule stripes

“…2A, D, G, J). These results confirmed previous investigations of the striped pattern of h, eve, run, and ftz in the gt mutant background (Hooper et al, 1989;Small et al, 1991;Klingler and Gergen, 1993;Carrol and Scott, 1986). The expression patterns of reporter genes containing cis-regulatory modules (CRMs) responsible for eve 2, h 5, eve 5, run 5 and ftz in gt À background also confirmed gt repression of specific pair-rule stripes (Small et al, , 1992Riddihough and Ish-Horowicz, 1991;Fujioka et al, 1999;Klingler et al, 1996;Calhoun and Levine, 2003).…”

“…Experimental evidence further supports the hypothesis of a Gt partner. In the wild-type eve 2 CRM, there are three Gt-binding sites mapped by footprinting analysis (Stanojevic et al, 1991;Small et al, 1991). The simultaneous deletions of all these sites in the context of the eve 2 CRM direct the anterior expansion of the lacZ reporter gene pattern, which is consistent with the expected repressive role of Gt (Small et al, 1992;Arnosti et al, 1996).…”

Chip interacts with diverse homeodomain proteins and potentiates Bicoid activity in vivo

“…Many, if not all of these stripes are also regulated by Bcd, even though most occur in regions with low to intermediate Bcd concentrations (39). The eve stripes are activated by several remote enhancers located Ϸ1.5-9 kb from the promoter (40,41) and Bcd-binding sites are critical for activation by at least the stripe 2 enhancer (42,43). It is likely, therefore, that Chip increases eve expression at least in part by increasing binding of Bcd to the enhancers.…”

Conversion of a silencer into an enhancer: evidence for a co-repressor in dorsal-mediated repression in Drosophila

“…Thus dl activity is influenced by the AT site and presumably the factor that occupies that site. (Small et al, 1991; for review on mechanisms of repression, see Jackson, 1991). We have begun to address the mechanism of dl-dependent repression.…”

“…The MSE P-transposon contains the 480 bp stripe 2 element from the eve promoter attached to a basal eve-lacZ fusion gene (Small et al, 1991). The MSE-lacZ fusion gene was inserted into the CaSpeR injection vector which contains the white gene as a selectable marker (Thummel et al, 1988).…”