Supplementary nuclear receptor NHR-60 is required for normal embryonic and early larval development of Caenorhabditis elegans.

The C. elegans genome encodes an unexpectedly large number of NHRs, the majority of which are classified as supplementary nuclear receptors (supnrs) that are likely to have evolved from an ancestral protein related to vertebrate HNF-4. To understand the need for this large repertoire of potential ligand-activated transcription factors, we have begun to study an 18-member subgroup defined by DNA binding domain relatedness. Here we report on NHR-60, a supnr expressed ubiquitously throughout development with a distinct pattern of localization on the nuclear periphery. Both antibody staining and GFP reporter genes demonstrated high-level expression and accumulation of NHR-60 in seam cell nuclei that is dependent on NHR-23 activity. Interference with NHR-60 activity, by either RNAi or overexpression of a putative dominant negative isoform, results in embryonic and early larval lethality, including defects in seam cell development. This adds NHR-60 to the list of C. elegans NHRs playing important roles in development.

BIR-1, the homologue of human Survivin, regulates expression of developmentally active collagen genes in C. elegans.

BIR-1 and Survivin are highly conserved members of the inhibitor of apoptosis protein family that regulate cell division in nematodes and mammals and inhibit apoptosis in mammals. In the C. elegans genome, bir-1 is organized in an operon together with transcription and splicing cofactor CeSKIP (skp-1) and is highly expressed during embryogenesis as well as in non-dividing cells during larval development. Previously we have shown that BIR-1 regulates transcription and development and its loss-of-function phenotype overlaps with loss of function of CeSKIP and nuclear hormone receptor CHR3 (NHR-23). Here we searched for genes whose expression is affected by BIR-1 loss of function using whole-genome microarray experiments and identified several collagen genes as candidate targets of bir-1 inhibition in L1 larval stage. The decreased expression of selected collagen genes in bir-l-inhibited larvae was confirmed by quantitative RT-PCR. Next, we generated transgenic lines expressing bir-1 mRNA under a heat shock-regulated promoter and tested whether bir-1 overexpression has the potential to augment the expression of genes that showed decreased expression in worms treated with bir-1 RNAi. Overexpression of bir-1 resulted in a pronounced increase (2 to 5 times) of the expression of these genes. Our findings support the concept that BIR-1, a protein generally regarded as a mitotic factor, is involved in the regulation of transcription during normal development of C. elegans and has a strong ability to affect transcription of developmentally active genes if overexpressed.

Elevated and deregulated expression of HDAC3 in human astrocytic glial tumours.

Abnormal expression of histone deacetylases may contribute to the establishment of a cancer specific transcription profile. We examined expression of HDAC3 in human non-malignant gliosis and glial astrocytic tumours. Samples from four non-malignant gliosis and 17 astrocytic gliomas (six of grade II, one of grade III and ten of grade IV) removed for therapeutic purposes were assayed for HDAC3 expression at mRNA and protein levels. HDAC3 mRNA was detected in non-tumorous gliosis as well as in all examined glial tumours. Seven out of eleven examined high-grade tumours showed an elevated number of copies of HDAC3 mRNA. Western blot analysis detected high levels of expression of HDAC3 in the majority of the examined tumours. Immunohistochemistry and immunofluorescence made on a collection of 35 astrocytic tumours detected nuclear as well as cytoplasmic HDAC3 expression in all of those tumours. While the distribution of HDAC3 was both nuclear as well as cytoplasmic and moderate in intensity in non-malignant tissues and low-grade gliomas, high-grade tumours expressed HDAC3 in a focally deregulated pattern that included strongly pronounced cytoplasmic localization. Confocal microscopy and additional co-localization analysis detected nuclear HDAC3 in all tumours examined. We conclude that HDAC3 expression is elevated in human astrocytic tumours and its expression pattern is deregulated at the cellular level in high-grade gliomas.