Evidence for modification of lamin B by a product of mevalonic acid.

Previous work from this laboratory has shown that a derivative of mevalonic acid is post-translationally incorporated into a number of specific proteins in Swiss 3T3 cells. Neither the nature of the modification nor the identities of the modified proteins have been determined to date. Here we describe results concerning modified proteins of approximately 67 kDa from HeLa cells and Chinese hamster ovary cells. We show that these proteins are specific to the nucleus and remain associated with a Triton/salt-insoluble nuclear fraction. Furthermore, immunological studies demonstrate that one of the modified proteins comigrates on two-dimensional gels with lamin B, a structural protein associated with the nuclear envelope. Using antibodies directed against lamin B in an immunoprecipitation experiment, we further show that this mevalonic acid-modified protein specifically coprecipitates with lamin B. These results support the hypothesis that lamin B is modified by a derivative of mevalonic acid.