JBC, Vol. 252, Issue 2, 457-463, Jan, 1977
Purification of biologically active globin mRNA using cDNA-cellulose affinity chromatography
T. G. Wood and J. B. Lingrel
A complementary DNA (cDNA) copy of mouse globin mRNA was synthesized using
the RNA-dependent DNA polymerase from avian myeloblastosis virus and the
oligo(dT) covalently attached to cellulose as primer. All four
deoxyribonucleotide triphosphates, NaCl, the globin mRNA template, and an
oligo(dT) primer were required for optimal synthesis of cDNA. By saturating
the primer sites using a 3-fold excess of mRNA, sufficient concentrations
of immobilized cDNA could be synthesized to allow the hybridization
reactions to be performed using an excess of globin cDNA. Conditions which
permitted the annealing of globin mRNA to cDNA-cellulose were selected and
the sequence specificity for hybridization to cDNA-cellulose was determined
using 28 S ribosomal RNA, polyadenylic acid, and mouse L-cell RNA. Both
analytical and preparative applications of this chromatographic medium were
explored. When radioactively labeled poly(A)-containing 9 S RNA isolated
from nucleated erythroid cells was analyzed by affinity chromatography on
globin cDNA-cellulose, 46 per cent of the applied radioactivity hybridized
to the cDNA-cellulose column. Only 1 per cent of the labeled RNA was
retained by the column during reapplication of the unbound fraction, while
96 per cent of the bound RNA reannealed to cDNA-cellulose. Hybridizations
utilizing unfractionated RNA extracts from either mouse reticulocytes or
nucleated erythroid cells provided a one-step purification method for
globin mRNA sequences. The relative purity of the RNA isolated by
cDNA-cellulose affinity chromatography was determined by hybridization
kinetic analysis. The cDNA-bound fraction obtained from the unfractionated
RNA of either cell type was shown to have a Crt1/2 of 2.7 x 10-3. This
represents a 60-fold purification of the globin sequences present in
reticulocyte polysomal RNA and a 280-fold enrichment of the globin mRNA in
nucleated erythroid cells. Hybridization to cDNA-cellulose did not result
in any change in the sedimentation rate of globin mRNA. Furthermore,
experiments were performed which demonstrated that the globin mRNA isolated
by hybridization to cDNA-cellulose retained its biological activity when
assayed in a wheat germ cell-free lysate.