4] Relative transcription rates and mRNA levels for the two chains of type I procollagen

Abstract

This chapter discusses the relative transcription rates and mRNA levels for the two chains of type I procollagen. Type I collagen, the most abundant connective tissue protein in skin and bone, is composed of two αl chains and one α2 chain. These chains are derived from larger precursor polypeptides called pro-αl and pro-α2. For accurate determination of mRNA ratios, the probes used should be of the same size and should represent portions of the two mRNAs with similar base sequence and composition, but should not cross-hybridize to any appreciable extent. These criteria are met by the experimental conditions described in this chapter. With this technique, the ratio of pro-α1/pro-α2 mRNA has been consistently found to be about 2:1 in near confluent cultures of normal human fibroblasts. However, in some of the osteogenesis imperfecta fibroblasts examined the ratios deviate significantly from 2 : 1,2 an observation suggesting the presence of mutations that alter either the transcription of one of the genes or the processing of RNA transcripts,