Abstract
During meiotic prophase in the fission yeast Schizosaccharomyces pombe, the nucleus oscillates between the two ends of a cell. This oscillatory nuclear movement is important to promote accurate pairing of homologous chromosomes and requires cytoplasmic dynein. Dynein accumulates at the points where microtubule plus ends contact the cell cortex and generate a force to drive nuclear oscillation. However, it remains poorly understood how dynein associates with the cell cortex. Here we show that S. pombe Num1p functions as a cortical-anchoring factor for dynein. Num1p is expressed in a meiosis-specific manner and localized to the cell cortex through its C-terminal PH domain. The num1 deletion mutant shows microtubule dynamics comparable to that in the wild type. However, it lacks cortical accumulation of dynein and is defective in the nuclear oscillation as is the case for the dynein mutant. We also show that Num1p can recruit dynein independently of the CLIP-170 homolog Tip1p.
Highlights
In the fission yeast Schizosaccharomyces pombe, microtubules position the interphase nucleus at the middle of a cell (Drummond and Cross 2000; Tran et al 2001)
It has been proposed that microtubules, formed from the spindle pole body (SPB), generate a pulling force on the SPB by sliding along the cell cortex mediated by dynein anchored to it, which is likely to regulate the disassembly of microtubules at the cell cortex (Yamamoto et al 2001; Yamamoto and Hiraoka 2003)
Fission yeast have a possible homolog of the budding yeast Num1p: To investigate the mechanism for cortical anchoring of dynein at meiotic prophase, we searched the S. pombe genome database and found a putative gene (SPBC216.02) encoding a weak homolog of S. cerevisiae Num1p
Summary
In the fission yeast Schizosaccharomyces pombe, microtubules position the interphase nucleus at the middle of a cell (Drummond and Cross 2000; Tran et al 2001). It has been reported that the dynein light chain (encoded by dlc1) and the Glued subunit of dynactin are indispensable for the accumulation of the dynein heavy chain at the cortex (Miki et al 2002; Niccoli et al 2004) It remains largely unknown how dynein associates the cell cortex. During mitosis in budding yeast, the nucleus migrates to the mother-bud neck and into the neck (DeZwaan et al 1997) Both movements require interaction of microtubules with the cortex, and the latter process is mediated by sliding of microtubules along the bud cortex, which requires dynein and dynactin. JV421 JV422 JV471 JV545 JV626 JV627 JV650 JV656 JV681 JV897 JV898 JW327 JW652 JW785 JX648 JX650 JY450
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