Heterogeneously initiated transcription from the pre-B- and B-cell-specific mb-1 promoter: analysis of the requirement for upstream factor-binding sites and initiation site sequences.
The mb-1 gene, encoding a membrane immunoglobulin-associated protein, is developmentally regulated and expressed specifically in pre-B and mature B lymphocytes. Analysis of the TATA-less mb-1 promoter indicated that it directs initiation of transcription from multiple sites. Promoter sequences between -68 and +70 conferred the correct pattern of cell type-specific transcription upon a heterologous gene. Two nuclear factor-binding sites that are important for promoter function were identified between -59 and -38. Both sites interacted with ubiquitous nuclear factors in vitro. One of these factors was identified as Sp1. Multimerized copies of both factor-binding sites augmented expression from a heterologous minimal promoter in both lymphoid and nonlymphoid cells, suggesting that additional mb-1 promoter sequences are involved in determining the correct cell type specificity. Analysis of the heterogeneity of transcription initiation indicated that a mutation which increased the distance between upstream sequences and the region of initiation resulted in the utilization of a novel set of initiation sites. Moreover, an insertion of a TATA element into the mb-1 promoter at -30 biased initiation of transcription to +1 but did not abolish the use of the other sites. Mutation of an initiator sequence homology encompassing one of the major initiation sites had only a minor effect on its utilization. From these data, we conclude that upstream factor-binding sites in the TATA-less mb-1 promoter define a region in which initiation of transcription occurs at multiple sites.
Travis
A
A
Department of Microbiology, Howard Hughes Medical Institute, University of California, San Francisco 94143-0414.
Hagman
J
J
Grosschedl
R
R
D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology*; D001483:Base Sequence; D002454:Cell Differentiation; D002460:Cell Line; D003001:Cloning, Molecular; D005091:Exons; D015698:Genomic Library; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009841:Oligonucleotides; D011401:Promoter Regions, Genetic; D011947:Receptors, Antigen, B-Cell / Q000235:genetics*; D015183:Restriction Mapping; D016385:TATA Box; D014158:Transcription, Genetic; D014162:Transfection
D009841:Oligonucleotides; D011947:Receptors, Antigen, B-Cell