The relationship between hnRNA+-poly(A) and mRNA+-poly (A) in non-dividing human lymphocytes. Evidence for distinct synthetic pathways for mRNA precursor- and nonprecursor-hnRNA.
The processing of hnRNA+-poly(A) to mRNA+-poly(A) has been studied in resting lymphocytes from human peripheral blood. In pulse-chase experiments, two types of hnRNA+-poly(A) have been distinguished: the first is labeled predominantly with exogenous radioactive precursors supplied during the pulse, and the second incorporates primarily scavenged labeled precursors made available during a chase incubation. When the disappearance of both types of hnRNA+-poly(A) was quantitatively compared with the appearance of stable and labile mRNA+-poly(A), only 10% of the anticipated cytoplasmic material was actually obtained. Statistically, 90% of the poly(A)-bearing hnRNA molecules processed were degraded. The two types of hnRNA+-poly(A) were found to be functionally different. Pulse-labeled material was processed to poly(A)-bearing mRNA; "chase-labeled" molecules did not leave the nucleus and never served as precursors for cytoplasmic mRNA. The data fit a model in which there are distinct pathways for mRNA precursor- and nonprecursor-hnRNA+-poly(A).
D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000378:metabolism*; D008970:Molecular Weight; D009694:Nucleic Acid Precursors / Q000378:metabolism*; D011061:Poly A / Q000378:metabolism*; D012313:RNA / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism*
D009694:Nucleic Acid Precursors; D012333:RNA, Messenger; D011061:Poly A; D012313:RNA