Tea2p Is a Kinesin-like Protein Required to Generate Polarized Growth in Fission Yeast

Abstract

Cytoplasmic microtubules are critical for establishing and maintaining cell shape and polarity. Our investigations of kinesin-like proteins (klps) and morphological mutants in the fission yeast Schizosaccharomyces pombe have identified a kinesin-like gene, tea2 +, that is required for cells to generate proper polarized growth. Cells deleted for this gene are often bent during exponential growth and initiate growth from improper sites as they exit stationary phase. They have a reduced cytoplasmic microtubule network and display severe morphological defects in genetic backgrounds that produce long cells. The tip-specific marker, Tea1p, is mislocalized in both tea2-1 and tea2Δ cells, indicating that Tea2p function is necessary for proper localization of Tea1p. Tea2p is localized to the tips of the cell and in a punctate pattern within the cell, often coincident with the ends of cytoplasmic microtubules. These results suggest that this kinesin promotes microtubule growth, possibly through interactions with the microtubule end, and that it is important for establishing and maintaining polarized growth along the long axis of the cell.

Two Related Kinesins,klp5+andklp6+, Foster Microtubule Disassembly and Are Required for Meiosis in Fission Yeast

“…There may be a heightened sensitivity to changes in microtubule organization when the distance between the cell's ends is significantly increased. The T phenotype of tea2⌬ cells is also enhanced when the cells are longer (Browning et al, 2000).…”

“…The KIP2 homolog tea2 ϩ has previously been characterized; null mutants are viable but have short microtubules and often take on a "T" morphology (Browning et al, 2000). The klp⌬, tea2⌬ double and triple mutants were as viable as the parental single and double mutant strains.…”

“…Rather, it seems likely that cdc25 ϩ is interacting with an unidentified gene whose activity is normally buffered by klp5 ϩ or klp6 ϩ . A role for cdc25 ϩ in regulating microtubule behavior is also indicated by interactions between the cdc25-22 allele and several other kinesins, including klp2 ϩ (Sweezy and McIntosh, personal communication), and tea2 ϩ (Browning et al, 2000). Tubulin metabolism involves many different classes of genes, so the candidates for such a locus are numerous.…”

“…S. pombe also expresses tea2 ϩ , a member of the KIP2 subfamily, which promotes microtubule growth (Cottingham and Hoyt, 1997). Deletion of tea2 ϩ leads to unusually short microtubules and the mislocalization of the tip-specific marker Tea1p (Browning et al, 2000). This compromises the polarity of tea2⌬ cells, leading to their "T" shape.…”

“…The Schizosaccharomyces pombe genome encodes nine kinesin-related genes from seven subfamilies and one cytoplasmic dynein (Hagan and Yanagida, 1990;Pidoux et al, 1996;Yamamoto et al, 1999;Brazer et al, 2000;Browning et al, 2000;Troxell et al, 2001; pombe genome project). Among the kinesin subfamilies found in fission yeast, three have direct effects on microtubule dynamics and higher order microtubule organization (Goldstein and Philp, 1999).…”