Isolation of cDNA clones for the human transferrin receptor

A cDNA clone bank containing 30 000 clones was constructed from sucrose gradient-fractionated mRNA from human placenta. mRNA coding for transferrin receptor (TR) was enriched by polysome immuno-adsorbed chromatography with monospecific rabbit IgG and protein-A Sepharose. The library was screened for hybridisation to 32P-labelled cDNA synthesised from immunoselected TR mRNA and from poly(A)+ RNA of the polysome fraction that failed to bind to protein-A Sepharose. Plasmids isolated from colonies showing hybridisation only to the probe made from immunoselected mRNA were then subjected to hybrid selection. Two clones, pTR-48 and pTR-67, were able to hybridise the mRNA coding for the TR.