CELL BIOLOGY: Size Matters

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Science  16 Nov 2001:
Vol. 294, Issue 5546, pp. 1419c
DOI: 10.1126/science.294.5546.1419c

Keeping a cell's organelles the right size is not a trivial problem. Marshall and Rosenbaum examined how Chlamydomonas cells control the size of the flagellum—a hairlike projection sticking out from the surface of the cell, composed of a precisely defined array of microtubules. Flagellar length appears to be tightly regulated, but the mechanisms governing length have not been clear. It appears that flagellar components are in a state of constant turnover. The cell establishes a balance between assembly at the tip and turnover by regulating intraflagellar transport of the key microtubule component, tubulin, to the tip. Blocking tubulin transport allows turnover to proceed, while inhibiting assembly, and leads to the shrinkage and resorption of the flagellum. Thus, in this case, the cell uses steady state assembly-disassembly to define organelle size. Adjusting the set point for the steady state would allow the cell to change the length of its flagella when necessary and can explain the phenotype of mutant cells that possess unusually long or short flagella.—SMH

J. Cell Biol. 155, 405 (2001).

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