HP1 is a highly conserved heterochromatin associated protein implicated in gene silencing, nuclear organization and telomere integrity. HP1 family proteins are characterized by two conserved domains, the chromodomain, which mediates the interaction with methylated lysine 9 of histone H3, and the chromo shadow domain, which is involved in homodimerisation and the association with several nuclear proteins including Rb. In C.elegans there are two HP1 homologues, HPL-1 and HPL-2. We have previously shown by RNAi that
hpl-2 is required for the maintenance of a functional germline and for vulval development. More recently we have extended our studies to
hpl-1 and
hpl-2 deletion alleles.The
hpl-2(
tm1489) deletion allele results in temperature sensitive sterility and growth defects. Although deletion of
hpl-1 results in no obvious phenotype,
hpl-1(
ok1060);
hpl-2(
tm1489) double mutants show a temperature sensitive larval arrest. To identify genes which may act in pathways redundant with or antagonistic to HPL-2, we are performing an RNAi based screen looking for genes whose inactivation either enhances or suppresses
hpl-2 germline and/or somatic defects. So far we have identified one class of genes whose depletion by RNAi in an
hpl-2(
tm1489) background leads to larval arrest at 25<
sym05> and enhanced sterility at 20<
sym05>C, with no or much weaker effects on N2 animals. A second class of genes suppresses the sterility and growth defects of
hpl-2(
tm1489) single mutants, and the larval arrest of
hpl-1(
ok1060);
hpl-2(
tm1489) double mutants. Interestingly, within both class of modifiers we find conserved genes involved in chromatin modification and remodelling. This RNAi based approach will allow us to build a network of chromatin modifying proteins involved in different aspects of somatic and germline development.