Drosophila CtBP: a Hairy-interacting protein required for embryonic segmentation and Hairy-mediated transcriptional repression

Abstract

hairy is a Drosophila pair-rule segmentation gene that functions genetically as a repressor. To isolate protein components of Hairy-mediated repression, we used a yeast interaction screen and identified a Hairyinteracting protein, the Drosophila homolog of the human C-terminal-binding protein (CtBP). Human CtBP is a cellular phosphoprotein that interacts with the C-terminus of the adenovirus E1a oncoprotein and functions as a tumor suppressor. dCtBP also interacts with E1a in a directed yeast two-hybrid assay. We show that dCtBP interacts specifically and directly with a small, previously uncharacterized C-terminal region of Hairy. dCtBP activity appears to be specific to Hairy of the Hairy/Enhancer of split [E(spl)]/Dpn basic helix-loop-helix protein class. We identified a Pelement insertion within the dCtBP transcription unit that fails to complement alleles of a known locus, l(3)87De. We demonstrate that dCtBP is essential for proper embryonic segmentation by analyzing embryos lacking maternal dCtBP activity. While Hairy is probably not the only segmentation gene interacting with dCtBP, we show dose-sensitive genetic interactions between dCtBP and hairy mutations.

Conserved region 2 of adenovirus E1A has a function distinct from pRb binding required to prevent cell cycle arrest by p16INK4a or p27Kip1

“…To evaluate the contribution of the E1A carboxylterminus, we constructed two mutants containing: (i) a deletion removing the last 52 amino acids of E1A (DC52); and (ii) alanine substitutions in the C-terminal CtBP-interaction motif (LDL-A4) (Schaeper et al, 1995(Schaeper et al, , 1998. The biological function of CtBP is not yet clear, but data derived from studies in Drosophila suggest that it is a co-factor of transcriptional repressors like Hairy, Snail, Knirps, KruÈ ppel and Enhancer of split (Nibu et al, 1998a,b;Poortinga et al, 1998). Deletion mutants of E1A lacking the CtBPinteraction domain have enhanced tumorigenic potential suggesting that CtBP may be a negative regulator of E1A (Boyd et al, 1993).…”

Golgi Ribbon Unlinking: An Organelle-Based G2/M Checkpoint

“…Previous work has shown that RNAi depletion of the single Drosophila GRASP homologue (dGRASP) or its partner dGM130 does not lead to an apparent separation of the paired Golgi stacks. 12,51 Furthermore, the single CtBP/BARS homologue that exists in Drosophila (dCtPB) has been shown to mediate transcription repression regulating embryonic development, [67][68] but thus far, no link to the Golgi organization has been reported.…”

Quantitative contributions of CtBP-dependent and -independent repression activities of Knirps

“…Drosophila factors functionally characterized as short-range repressors all interact with CtBP, although it has not been established that all factors that bind the co-factor are necessarily short-range repressors. The longrange repressor protein Hairy, in particular, is thought to interact with CtBP, although this might be in an antagonistic mode (Poortinga et al, 1998;Zhang and Levine, 1999).…”