This is a proposal to study mechanisms of gene regulation during early development using the sea urchin histone gene family as a model system. This gene family includes two subfamilies, """"""""early"""""""" and """"""""late"""""""", that are regulated differently during sea urchin development. Early histone genes are expressed maximally from fertilization to the blastula stage, late histone genes from the blastula stage onwards. This stage-specific switch in histone gene expression is the result largely of modulations of early and late gene transcription rates.
The specific aims of this proposal are (1) to locate histone DNA sequences required for the regulation of early and late histone genes during development, and (2) to identify and characterize trans-acting effector molecules that are responsible for this regulation. Histone gene regulatory sequences will be localized by a mutagenesis-gene transfer approach involving microinjection of mutant histone gene constructs into sea urchin embryos and assessing the effects of such mutations on the timing of their expression during development. The analysis of trans-acting regulators of histone gene expression will comprise three related approaches: (1) further characterization of a sea urchin nuclear factor(s), termed H2b-f1, that stimulates sea urchin early and late H2b transcript accumulation in Xenopus oocytes, (2) examination of properties of histone gene regulatory factors by competition between microinjected DNA and endogenous or coinjected histone genes for trans-acting regulatory molecules, in vivo (in the sea urchin); (3) use of """"""""genomic sequencing"""""""" for the direct examination of interactions between putative histone gene regulatory factors and histone genes in vivo. Together, these several approaches will provide a detailed picture of the control of sea urchin histone gene expression by effector molecules that interact with DNA. The proposed research is of fundamental importance to understanding molecular-genetic mechanisms underlying embryonic development. Consequently, it may prove useful in understanding of diseases, such as cancer that may result from aberrations in developmental regulatory processes.
|Tan, H; Ransick, A; Wu, H et al. (1998) Disruption of primary mesenchyme cell patterning by misregulated ectodermal expression of SpMsx in sea urchin embryos. Dev Biol 201:230-46|
|Dobias, S L; Ma, L; Wu, H et al. (1997) The evolution of Msx gene function: expression and regulation of a sea urchin Msx class homeobox gene. Mech Dev 61:37-48|
|Ma, L; Swalla, B J; Zhou, J et al. (1996) Expression of an Msx homeobox gene in ascidians: insights into the archetypal chordate expression pattern. Dev Dyn 205:308-18|
|Char, B R; Tan, H; Maxson, R (1994) A POU gene required for early cleavage and protein accumulation in the sea urchin embryo. Development 120:1929-35|
|Chen, J; Maxson, R; Jones, P A (1993) Direct induction of DNA hypermethylation in sea urchin embryos by microinjection of 5-methyl dCTP stimulates early histone gene expression and leads to developmental arrest. Dev Biol 155:75-86|
|Char, B R; Bell, J R; Dovala, J et al. (1993) SpOct, a gene encoding the major octamer-binding protein in sea urchin embryos: expression profile, evolutionary relationships, and DNA binding of expressed protein. Dev Biol 158:350-63|
|Bell, J; Char, B R; Maxson, R (1992) An octamer element is required for the expression of the alpha H2B histone gene during the early development of the sea urchin. Dev Biol 150:363-71|
|Zhao, A Z; Vansant, G; Bell, J et al. (1991) Activation of the L1 late H2B histone gene in blastula-stage sea urchin embryos by Antennapedia-class homeoprotein. Mech Dev 34:21-8|
|Zhao, A Z; Colin, A M; Bell, J et al. (1990) Activation of a late H2B histone gene in blastula-stage sea urchin embryos by an unusual enhancer element located 3' of the gene. Mol Cell Biol 10:6730-41|
|Ito, M; Sharma, A; Lee, A S et al. (1989) Cell cycle regulation of H2b histone octamer DNA-binding activity in Chinese hamster lung fibroblasts. Mol Cell Biol 9:869-73|