Beschreibung:
<jats:p>
Highly purified globin mRNA from ducks was copied with RNA-directed DNA polymerase from avian myeloblastosis virus into anti-messenger DNA. With excess RNA, more than 90% of this DNA annealed back to its template with a C
<jats:sub>o</jats:sub>
t/2 value of 7.5 × 10
<jats:sup>-4</jats:sup>
mol·sec· liter
<jats:sup>-1</jats:sup>
; the melting temperature of the hybrid was 86°. Giant nuclear RNA fractions with sedimentation coefficients of more than 50 S formed hybrids of almost equal stability at C
<jats:sub>o</jats:sub>
t/2 values of 0.05-0.42 mol·sec· liter
<jats:sup>-1</jats:sup>
, indicating amRNA content of 0.3-1.5%. 12S RNA from the same polyribosomes and nuclear giant RNA from HeLa cells did not cross-hybridize. Although a large part of the giant RNA broke down in 99% dimethylsulfoxide gradients, RNA fractions sedimenting faster than 28S rRNA still were found to consist of up to 0.03% globin mRNA sequences. Thus, the mRNA sequences are contained in the covalent structure of giant nuclear precursors, which are termed precursor-mRNA.
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