Lecture 19

The eve stripe 2 enhancer employs multiple modes of transcriptional synergy

Today we will be discussing the following paper:

Arnosti DN, Barolo S, Levine M, Small S.
The eve stripe 2 enhancer employs multiple modes of transcriptional synergy.
Development. 1996 Jan;122(1):205-14.

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Introduction:

    This study builds on the two previous studies we discussed in lecture 17 and 18.  In the more recent study (EMBO 11, 4047-57, 1992) along with other publications, it was shown that repressors bound to the minimal stripe enhancer (MSE) only affected stripe two, and didn't affect stripe 3.  This phenomenon was termed short range repression.

We know that Gt specifies the anterior border of eve stripe 2.  The main question is how?

The hypothesis is that Bcd is limiting, so that the MSE is sensitized to repression by Gt.

Today's paper investigates the role of strong and weak Bcd binding sites in activation, and then asks how Gt might affect Bcd.

One of the questions posed by this paper is whether activation requires Bcd or Hb specifically, or whether heterologous activators can substitute.  It appears that activation is not dependent on specific activators but rather, it appears to depend on having enough activators bound.