Association of a polyuridylate-specific endoribonuclease with small nuclear ribonucleo-proteins which had been isolated by affinity chromatography using antibodies from a patient with systemic lupus erythematosus.
Immunoglobulins, containing antibodies against U1-snRNP, have been prepared from a patient with systemic lupus erythematosus. After coupling these antibodies to a Sepharose matrix, U-snRNPs have been isolated and purified from rat liver nuclei by use of immunoaffinity chromatography. The resulting RNPs had the typical protein pattern of U-sn RNPs and a sedimentation coefficient of 12 S. The U-snRNP preparation was associated with an endoribonuclease which required Mg2+ for optimal activity. The enzyme, with an pH optimum of 6.2, degraded only poly(U). Other single-stranded polyribo- and polydeoxyribonucleotides, tRNA, as well as double-stranded RNA and DNA were not digested. The products of a terminal digestion are (U)6-12 with 3'-OH and 5'-P termini. The possible involvement of this endoribonuclease in the splicing of hnRNA is discussed.
D000818:Animals; D000974:Antibodies, Antinuclear / Q000302:isolation & purification; D000915:Antibody Affinity; D002846:Chromatography, Affinity; D004722:Endoribonucleases / Q000302:isolation & purification*; D006801:Humans; D007120:Immunochemistry; D007074:Immunoglobulin G / Q000302:isolation & purification; D008099:Liver / Q000201:enzymology*; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D008297:Male; D011072:Poly U / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012261:Ribonucleoproteins / Q000302:isolation & purification*; D017411:Ribonucleoproteins, Small Nuclear; D013379:Substrate Specificity
D000974:Antibodies, Antinuclear; D007074:Immunoglobulin G; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; D011072:Poly U; D004722:Endoribonucleases