标题：Heterogeneous nuclear RNA secondary structure: oligo (U) sequences base-paired with poly (A) and their possible role as binding sites for heterogeneous nuclear RNA-specific proteins
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：4
页码：1426-1430
DOI：10.1073/pnas.74.4.1426
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：HeLa cell heterogeneous nuclear RNA derived from high-molecular-weight nuclear ribonucleoprotein (RNP) particles contains oligo(U) sequences of 15-50 nucleotides base-paired with poly(A). These duplexes are resistant to pancreatic RNase at 0.5 M NaCl in native RNP, remain so after chemical deproteinization of the RNP digests, and then copurify with poly(A) on oligo(dT)-cellulose chromatography. Oligo(dT)-cellulose binding capacity of the oligo(U)-poly(A) duplexes is abolished by prior titration of the nonduplex poly(A) regions with excess poly(U). The oligo(dT)-purified fraction is 97.5 mole % A + U and the [3H]uridine-labeled component is resistant to redigestion by pancreatic RNase at 0.5 M NaCl but not at 0.01 M NaCl. After thermal denaturation, the [3H]uridine-labeled chains become RNase-sensitive at 0.5 M NaCl. Electrophoresis of [3H]adenosine- or [3H]uridine-labeled material in polyacrylamide gels containing 99% formamide confirms that the oligo(U) sequences are not covalently linked to poly(A). Controls establish that the A-U duplexes are not formed artifactually during isolation of heterogeneous nuclear RNP or subsequent fractionation. The oligo(U)-poly(A) duplexes appear to be associated with protein in native heterogeneous nuclear RNP, as reflected by the differential pancreatic RNase sensitivity of the duplexed oligo(U) in RNP (resistant) and RNA (sensitive), measured at physiological ionic strength.
