Characterization of the human granulocyte-macrophage colony-stimulating factor promoter region by genetic analysis: correlation with DNase I footprinting.

T-cell activation induces expression of the hematopoietic growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF). To define the molecular events involved in the induction of GM-CSF gene expression more clearly, we prepared and analyzed deletion mutants of GM-CSF promoter recombinant constructs. The results localized inducible expression to a 90-base-pair region (-53 to +37) which is active in uninfected and human T-cell leukemia virus-infected T-cell lines but not in resting or mitogen-stimulated B cells. DNase I footprinting experiments revealed protection of sequences contained within this region, including a repeated nucleotide sequence, CATT(A/T), which could serve as a core recognition sequence for a cellular transcription factor. Upstream of these GM-CSF promoter sequences is a 15-base-pair region (-193 to -179) which has negative regulatory activity in human T-cell leukemia virus-infected T cells. These studies revealed a complex pattern of regulation of GM-CSF expression in T cells; positive and negative regulatory sequences may play critical roles in controlling the expression of this potent granulopoietin in the bone marrow microenvironment and in localized inflammatory responses.

A simple fractionation of chicken egg yolk yields a protein component that stimulates cell proliferation and differentiation in primary avian tendon cells.

An easily prepared and stable protein fraction from chick egg yolk promotes cell division (40 h generation time) and expression of procollagen (60% of total protein synthesis) in primary avian tendon cells in a serum-free medium. The activity of this yolk fraction (YF) is proteinaceous as reflected by its sensitivity to protease treatment. Yolk fraction is resolved into four major components on sodium dodecyl sulfate polyacrylamide gel electrophoresis with apparent molecular weights of 82,70,42,35 (X 10(-3)). Under nondenaturing conditions, YF runs as a mixture of high molecular weight aggregates on Sephacryl G-200. We postulate that the active part of YF could be the in ovo growth promoter for embryonic chick tendon cells.