RESUMO
Identification of transcribed sequences by cDNA selection is a potentially rapid and efficient way of scanning large genomic DNA fragments for the presence of genes. To evaluate this approach further, we have applied it to three yeast artificial chromosomes (YACs) and examined the products obtained from a total of about 1100 kb from two regions of the human major histocompatibility complex (MHC). One YAC was derived from an extensively studied portion of the Class II region of the MHC. The cDNAs recovered from this YAC included representatives of the previously described genes as well as one or more cDNA clones not described in the databases. A second YAC spanned about 330 kb of DNA surrounding the Class I gene HLA-A. In addition to Class I clones, 10 distinct cDNA products were identified from this YAC. A third YAC contained about 700 kb of human DNA, including 260 kb of overlap with the second YAC, and recovered an additional cDNA complementary to YAC B30 H3 DNA. Overall, the method is shown to be able to detect very scarce cDNAs and to detect a large fraction of coding sequences in YAC clones. Advantages and limitations of the approach are discussed.
Assuntos
DNA Complementar/genética , Técnicas Genéticas , Complexo Principal de Histocompatibilidade , Mapeamento Cromossômico , Cromossomos Artificiais de Levedura , Clonagem Molecular , Estudos de Avaliação como Assunto , Genes MHC Classe I , Genes MHC da Classe II , Genoma Humano , Antígenos HLA/genética , HumanosRESUMO
The Contingent replication assay (CRA) is a rapid assay for the screening and isolation of cDNAs by protein-protein or protein-DNA interactions in mammalian cells. The method has been shown to enrich a plasmid containing a cDNA encoding the bacterial replication-related protein, R6K, from a mixture of two plasmids. In this report we present data illustrating the sensitivity and selectivity of the method. Using the small subunit of TFIIF (Rap30) as a target, we demonstrate the enrichment of a clone encoding the large subunit, Rap74, from a cDNA library. Additional cDNA clones including human Rap30 and an anonymous cDNA clone homologous to members of the human cdc2 kinase family were enriched and isolated by a modified screening approach. The structure of these additional clones suggest that the CRA enriches for products that interact not only directly with the target protein but also through bridging by endogenous proteins.
