ABSTRACT
Interleukin-1 beta (IL-1 beta) mediates a wide range of immune and inflammatory responses. The active cytokine is generated by proteolytic cleavage of an inactive precursor by a protease called the IL-1 beta converting enzyme (ICE). A cDNA encoding this protease was recently isolated. A human genomic clone containing the ICE gene (IL1BC) was isolated using the cDNA as a probe. The gene consists of 10 exons spanning at least 10.6 kb. 5'-anchored polymerase chain reaction indicated a single transcription start site approximately 33 bp upstream of the initiator Met codon. The 5'-flanking region does not have an apparent TATA box but may contain an initiator (Inr) promoter element. However, transcriptional activity could not be detected with a fusion gene containing the 5'-flanking region linked to the bacterial chloramphenicol acetyltransferase gene (CAT) when transfected into the human acute monocytic leukemia cell line THP-1. Using the genomic IL1BC clone, we have confirmed the localization of the gene to chromosome 11 band q22.2-q22.3 by fluorescence in situ hybridization.
Subject(s)
Chromosomes, Human, Pair 11 , Hominidae/genetics , Metalloendopeptidases/genetics , Amino Acid Sequence , Animals , Base Sequence , Caspase 1 , Chromosome Banding , Chromosome Mapping , Cloning, Molecular , Codon , DNA Primers , DNA Probes , Exons , Genomic Library , Humans , In Situ Hybridization , Introns , Molecular Sequence Data , Polymerase Chain Reaction , Promoter Regions, Genetic , TATA Box , Transcription, GeneticABSTRACT
Cloning of a ligand for the murine flt3/flk-2 tyrosine kinase receptor was undertaken using a soluble form of the receptor to identify a source of ligand. A murine T cell line, P7B-0.3A4, was identified that appeared to express a cell surface ligand for this receptor. A cDNA clone was isolated from an expression library prepared from these cells that was capable, when transfected into cells, of conferring binding to a soluble form of the flt3/flk-2 receptor. The cDNA for this ligand encodes a type I transmembrane protein that stimulates the proliferation of cells transfected with the flt3/flk-2 receptor. A soluble form of the ligand stimulates the proliferation of defined subpopulations of murine bone marrow and fetal liver cells as well as human bone marrow cells that are highly enriched for hematopoietic stem cells and primitive uncommitted progenitor cells.
