Mammalian
p300 and CBP are closely related Histone Acetyltransferases (HATs) serving as integrators of multiple positive and negative signaling pathways. Recently, we have shown that a C. elegans gene closely related to
p300/CBP,
cbp-1, is required to specify multiple differentiation events during embryogenesis.
cbp-1(RNAi) embryos display substantial hyperproliferation and a complete lack of tissue specification with the exception of ectopical neural differentiation, implicating that CBP-1 is involved in specifying hypodermal as well as endodermal and mesodermal cell fates (1). To further investigate the mechanisms underlying the differentiation-promoting activities of CBP-1, we isolated a
cbp-1 deletion mutant using a PCR-based approach. Embryos homozygous for the
cbp-1 deletion mainly die around the R-fold stage, suggesting that maternally provided CBP-1 is sufficient for the initiation of most differentiation events.Delta-
cbp-1 gives rise to a truncated protein lacking the Histone-Acetyltransferase (HAT) activity possessing domain of the protein. Using RNAi specifically targeting the wt version of the protein in delta-
cbp-1 heterozygous animals, we could show that the isolated deletion represents a functional null allele, underscoring the central role of the HAT domain for the functionality of CBP-1. By means of injecting animals heterozygous for delta-
cbp-1 with a YAC as a source for an intact copy of
cbp-1 we obtained maternal as well as zygotic rescue. Embryos losing maternal expression phenotypically closely resemble the phenotype observed in the
cbp-1(RNAi) embryos. A detailed analysis of these embryos as compared to the
cbp-1(RNAi) and delta-
cbp-1 embryos will be discussed at the meeting. Domains that have been implicated in
p300 function in other systems, including the HAT-domain, will be mutagenized in vitro and reintroduced into the
cbp-1-containing YAC. Subsequent rescue experiments and comparison of the phenotypes obtained upon loss of maternal expression will help to identify regions of CBP-1 that are accountable for the failure of various tissues to differentiate. First results will be presented. Furthermore, trying to understand the role of CBP-1 in differentiated tissues including neurons, we employed tissue-specific and hs-inducible RNAi. An analysis of the phenotypes obtained will be discussed. 1. Mello, C. and Shi, Y. (1998), A CBP/p300 homolog specifies multiple differentiation pathways in Caenorhabditis elegans. Genes Dev., (7), 943-55.