Eubacterial components similar to small nuclear ribonucleoproteins: identification of immunoprecipitable proteins and capped RNAs in a cyanobacterium and a gram-positive eubacterium.
Small nuclear ribonucleoprotein (snRNP) particles play an important role in the processing of pre-mRNA. snRNPs have been identified immunologically in a variety of cells, but none have ever been observed in prokaryotic systems. This report provides the first evidence for the presence of snRNP-like components in two types of prokaryotic cells: those of the cyanobacterium Synechococcus leopoliensis and those of the gram-positive eubacterium Bacillus subtilis. These components consist of snRNP-immunoreactive proteins and RNAs, including some with the snRNP-unique 5' m2,2,7G (m3G) cap. Immunoreactivity was determined by immunoprecipitation procedures, with either antinuclear-antibody-positive (RNP- and Sm-monospecific) patient sera or a m3G monoclonal antibody, with radiolabelled cell extracts that were preadsorbed with antinuclear-antibody-negative sera. S. leopoliensis immunoprecipitates showed the presence of high-molecular-mass proteins (14 to 70 kDa) and RNAs (138 to 243 nucleotides) that are analogous in size to proteins and RNAs found in human (HEp-2) cell immunoprecipitates but absent in Escherichia coli immunoprecipitates. Thin-layer chromatography of S. leopoliensis immunoprecipitates confirmed the presence of a capped nucleotide similar to a capped nucleotide in HEp-2 immunoprecipitates; no such nucleotide was observed in E. coli immunoprecipitates. Immunoreactive RNAs (117-170 nucleotides) were identified in a second eubacterium, B. subtilis, as well. This work suggests that snRNPs or their evolutionary predecessors predate the emergence of eukaryotic cells.
Kovacs
S A
SA
Department of Biology, California State University, Fresno 93740.
O'Neil
J
J
Watcharapijarn
J
J
Moe-Kirvan
C
C
Vijay
S
S
Silva
V
V
D000974:Antibodies, Antinuclear / Q000276:immunology; D001412:Bacillus subtilis / Q000737:chemistry* / Q000276:immunology; D002478:Cells, Cultured; D000458:Cyanobacteria / Q000737:chemistry* / Q000276:immunology; D004926:Escherichia coli / Q000737:chemistry / Q000276:immunology; D006801:Humans; D011233:Precipitin Tests; D011387:Prokaryotic Cells / Q000737:chemistry / Q000276:immunology; D012315:RNA Caps / Q000302:isolation & purification*; D012342:RNA, Small Nuclear / Q000302:isolation & purification*; D017411:Ribonucleoproteins, Small Nuclear / Q000276:immunology / Q000302:isolation & purification*
D000974:Antibodies, Antinuclear; D012315:RNA Caps; D012342:RNA, Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear