CCT chaperonin在線蟲早期胚胎發育的功能分析

Abstract

CCT (Chaperonin contain T-complex polypeptide 1又名TriC)是真核生物特有的chaperonin，由8個次單元組成，共組一個16-mer的雙環結構複合體，協助新合成蛋白的摺疊或是變性蛋白的再褶疊。目前已知actin，tubulin，以及其它蛋白經過CCT摺疊而活化。且陸續有新的蛋白發現和CCT作用，其中，許多是具有WD repeat doamain的蛋白。CCT各次單元序列之間的差異，暗示各單元扮演不同的功能，可能和不同受質作用。我们在線蟲( Caenorhabditis elegans)分別對各次單元進行knockdown，發現這些基因皆為早期胚胎發育所需，細胞分裂時，如紡錘絲的形成，染色體的分離，細胞質分裂等過程都受到影響，表現pleiotropic的性狀。我们的觀察顯示tubulin的表現量可能減少。然而，我们發現knockdown後，線蟲會滯留在幼蟲時期，生殖腺退化，且消化道澎大並充滿未消化的細菌，對機械性外力敏感。這些性狀和let-363(CeTOR)突變株有相似之處。TOR是細胞生長的中心調控者，負責生合成核醣體，轉譯等作用。因此，我们猜測CCT可能影響細胞的生長與代謝。

Eukayotic chaperonin CCT (Chaperonin contain T-complex polypeptide also named TriC)，established by 8 subunits，is a 16- mer double-ring complex. CCT contributes to the folding of newly synthesized proteins and the refolding of denatured proteins. Actin, tubulin and several other proteins are well known activated by CCT folding. New proteins are still found to interact with CCT, and many of them WD repeat proteins. CCT subunits are different in protein sequences, suggesting specification between them. We knockdown the subunits in Caenorhabditis elegans and found them all essential for early embryogenesis. We found defects in spindle fiber formation，chromosome segregation，cytokinesis and others，indicating a pleiotropic effect. Our observation also suggests deficiency in tubulin. However, the progeny arrest in larval stage with degenerate gonads and intestinal lumens enlarged by undigested bacteria. And they are sensitive to mechanical pressure. Similar phenotypes are in let-363 (CeTOR) mutant. TOR is the central controller of cell growth. We suggest a role of CCT in cell growth and metabolism.