Our work is focussed on the molecular mechanisms responsible for establishing and maintaining stable states of gene expression during vertebrate embryogeneis. Progress has been achieved in the following key areas: 1. We have determined that nucleosome mobility has a key role in facilitating transcription of chromatin templates and that linker histones repress transcription by restricting this mobility. 2. We have determined that chromatin structure has an essential role together with Xenopus heat shock transcription factor in regulating Xenopus hsp70 gene transcription in Xenopus oocytes. 3. We have determined that DNA methylation does not influence the association of linker histones with DNA, and that incorporation of HMG14 and 17 into nucleosomes during chromatin assembly does influence chromatin compaction. 4. We have found that nucleosome dilution in vitro can facilitate transcription factor access to nucleosomal DNA in vitro. 5. We have examined the nucleic acid binding specificities of two proteins capable of interacting with either DNA or RNA. TFIIIA which binds specifically to 5S rRNA and 5S DNA, does not interact specifically with RNA-DNA heteroduplexes countaining 5S RNA and DNA sequences. FRGY2 is found to recognize specific RNA sequences via the highly conserved cold shock domain.