Nuclear granules recognized by some monoclonal antibodies against intermediate filament protein locate on chromosomes during mitosis

AC54 monoclonal antibody (MAb), an anti-desmin MAb, recognizes both intermediate filaments (IFs) and nuclear granules in BHK21/C13 cells. To investigate nuclear granules, similar MAbs were obtained by using desmin fraction as an antigen. Among them, DSB389 MAb recognized mainly nuclear granules in HeLa and rat liver cells. The nuclear granules in HeLa cells were aligned in arrays, sometimes connected by, or part of, a rope-like structure, and stable against treatment with 0.5% Triton X-100 and 2 M NaCl. They located on or around the chromosomes during mitosis. Essentially the same results were obtained with DSB860 and AC54 MAbs. The distribution of the granules in liver nuclei recognized by DSB389 MAb was similar to that of DNA and was different from that of the nuclear pore complexes. The biological significance of the nuclear granules is discussed.