6th ESACP Congress, Heidelberg, April 7-11, 1999

A039
KINETICS OF CELL-DERIVED DOUBLE-STRANDED RIBONUCLEIC ACIDS DURING DIFFERENTIATION
Bruvere R, Pilmane M, Feldmane G, Volrate A, Loza V

Biomedical Research and Study Centre, University of Latvia; Medical Faculty, University of Latvi; Institute of Microbiology and Virology, Riga, Latvia

Double-stranded ribonucleic acids (dsRNA)exhibit multiple biological activities including the regulation of cell growth and differentiation. In this investigation the formation of dsRNA was studied in differentiating cells that after fixation were treated or non-treated with proteinase K. Fluorescent in situ immuno- assay by using highly specific monoclonal antibodies against the A-helix structure of natural dsRNA was performed. These antibodies do not react with single-stranded (ss) dsRNA, ss- or dsRNA, RNA-DNA hybrids, short helical regions which are present in tRNA, 5S RNA, 7S RNA, and viroids. As demonstrated on the retinoic acid-induced differentiating mouse Neuro-2a cells treated with proteinase K, dsRNA structures first appear in nucleus, then surround the nuclear envelope, and finally enter the cytoplasm. The intra- cellular presence of dsRNAs has a limited span of existence, because the completely differentiated cells do not contain dsRNA nor in cytoplasm or nuclei, although secondary appearence of dsRNA in nucleoli of senescent cells are evident. In cells non-treated with proteinase K, dsRNAs are seen only in nuclei as a ring located near the nuclear envelope. Our findings suggest that in differentiating Neuro-2a cells, dsRNA displays complex spatial and temporal organization being un-linked to proteins only when located nearly to the nuclear envelope.