Several fission yeast temperature-sensitive mutants defective in pre-mRNA processing (prp- mutants) at the nonpermissive temperature have been identified. Here, the prp2+ gene has been cloned by its ability to complement the temperature-sensitive growth defect of a prp2- mutant. The gene also corrects the pre-mRNA splicing defect of prp2- mutants and encodes a 59-kilodalton polypeptide (PRP2). A molecular characterization indicates that PRP2 is a previously uncharacterized yeast splicing factor with extensive similarity to the mammalian splicing factor U2AF65. Thus, this study provides evidence that a U2AF homolog participates in RNA processing in vivo.

No abstract

The trabecular meshwork (TM), a specialized eye tissue, is a major site for regulation of the aqueous humor outflow. Malfunctioning of this tissue is believed to be responsible for development of glaucoma, a blinding disease. Myocilin is a gene linked to the most common form of glaucoma. The protein product has been localized to both intra and extracellular sites, but its function still remains unclear. This study was to determine whether extracellular myocilin presented in the matrix affects adhesion, morphology, and migratory and phagocytic activities of human TM cells in culture. Cell adhesion assays indicated that TM cells, while adhering readily on fibronectin, failed to attach on recombinant myocilin purified from bacterial cultures. Adhesion on fibronectin was also compromised by myocilin in a dose dependent manner. Myocilin in addition triggered TM cells to assume a stellate appearance with broad cell bodies and microspikes. Loss of actin stress fibers and focal adhesions was observed. TM cell migration on fibronectin/myocilin to scratched wounds was reduced compared to fibronectin controls. Myocilin, however, had little impact on phagocytic activities of TM cells. Cell attachment on fibronectin and migration of corneal fibroblasts, a control cell type, were not altered by myocilin. These results demonstrate that extracellular myocilin elicits anti-adhesive and counter-migratory effects on TM cells. Myocilin in the matrix of tissues could be exerting a similar influence on TM cells in vivo, impacting the flexibility and resilience required for maintenance of the normal aqueous outflow.