Transcription regulatory networks in Caenorhabditis elegans

cpn-3 encodes a calponin homolog, most closely related to its paralog CPN-4 in C. elegans; CPN-3 is more similar to the calponin paralogs transgelin (SM22 alpha) or neuronal protein NP25 than to calponin per se.

cpr-4 encodes a cathepsin B-like cysteine protease expressed at all life stages.

csn-5 encodes an ortholog of subunit 5 of the COP9 signalosome complex (CSN5), which in turn is a pan-eukaryotic multiprotein complex that positively regulates E3 ubiquitin ligases, physically interacts with SCF-type E3 ubiquitin ligases, and probably regulates protein degradation; CSN-5 (along with KGB-1 and ZYX-1) physically binds germline RNA helicases (GLH proteins), and csn-5(RNAi) results in sterile worms with small gonads and no oocytes, causing oogenesis to cease, but not affecting the initial assembly of P granules -- a defect essentially identical to that produced by RNAi with a combination of glh-1 and glh-4.

The ctb-1 gene resides on the mitochondrial chromosome, and encodes the cytochrome b protein of mitochondrial complex III; mutation of ctb-1 suppresses the slow embryonic development of isp-1 mutants, while enhancing their paraquat resistance.

cts-1 encodes a citrate synthase, predicted to be mitochondrial, that is required for embryonic development.

cul-3 encodes one of six C. elegans cullins; by homology, CUL-3 is predicted to interact with a RING-finger protein to form the catalytic core of an SCF-type E3-ubiquitin ligase complex required for the ubiquitination and degradation of target proteins; in the early embryo, maternal CUL-3 is essential for degradation of MEI-1, a meiosis-specific subunit of the microtubule-severing katanin complex that is active during meiosis but whose degradation is essential for successful mitotic spindle formation and subsequent zygotic cytokinesis; to effect MEI-1 degradation, CUL-3 interacts with MEL-26, a substrate-specific adaptor protein that also binds MEI-1, thus linking MEI-1 with the CUL-3-containing E3 ligase; CUL-3 activity is regulated by cycles of neddylation and deneddylation that are dependent upon activity of the DCN-1, RBX-1, and RFL-1 gene products; cul-3 mRNA is present at all life stages, with highest levels seen in embryos; expression of a cul-3::GFP transcriptional reporter fusion is detected in many somatic tissues, including the pharynx, intestine, hypodermis, and several different muscle types.

The primary phenotype of cup-2 animals is an accumulation of secreted GFP in the pseudocoelom, suggesting a decrease in, or the absence of, endocytosis in coelomocytes.