Structures of introns of human mDNA

Abstract

We confirmed many introns of human mRNA other than gt//ag (namely, those whose D- and A- ends are gt and ag, respectively), and in order to systematically treat them, we tried to expand the GTAG rule to cover the introns of g//g containing gc//ag (19 cases), gt//gg (11), gt//cg (4), and gg//ag (3) as well as gt//ag (> 5600). Some introns of other kinds, sucu as [ga//ac] also are reported. We found parts of necessary conditions that a new GG rule requires, as follows: (i) A necessity of the second bases at the D-end is carbonyl group, especially on the pyrimidine ring, and especially at the 2-position, (ii) A second base at the A-end requires an amino group especially on the purine ring, and the more carbonyl groups, the more disadvantageous, and (iii) The bases at A-ends appear to be a little more effective than D-ends. Existance of the third kind of splicing pathway is suggested.