Immunofluorescence localization of HeLa cell microtubule-associated proteins on microtubules in vitro and in vivo.

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Abstract
Rabbit antisera were prepared against the 2 major groups of microtubule-associated proteins (MAP) from HeLa [human cervical carcinoma] cells, proteins of .apprx. 210,000 MW (210k MAP), and 125,000 MW (125k MAP). These antisera were characterized by a sensitive antigen detection technique employing immunofluorescence to localize cross-reactive material in polyacrylamide gels. Antisera prepared against the 210k MAP showed no cross-reactivity with extract proteins of other MW or with brain MAP, but did react with proteins of 210,000 MW and with a minor HeLa MAP of .apprx. 255,000 MW. Antibodies prepared against the 125k HeLa MAP reacted specifically with proteins of 125,000 MW, showing no cross-reactivity with other HeLa extract proteins or porcine brain MAP. Immunofluorescence with the 210k and 125k MAP antisera was used to demonstrate the association of each of the MAP with fixed HeLa microtubules in vitro. Immunofluorescence with these antisera revealed a physical association of 210k and 125k MAP with a Colcemid-sensitive fiber network in fixed interphase and mitotic HeLa cells. Using specific antisera to the 2 major groups of HeLa MAP, these proteins were characterized as components of microtubules in HeLa cells.