Expression of mRNA encoding the macrophage colony-stimulating factor receptor (c-fms) is controlled by a constitutive promoter and tissue-specific transcription elongation.

Abstract

The gene encoding the receptor for macrophage colony-stimulating factor 1 (CSF-1), the c-fins protooncogene, is selectively expressed in immature and mature mononuclear phagocytes and trophoblasts. Exon 1 is expressed only in trophoblasts. Isolation and sequencing of genomic DNA flanking exon 2 of the murine c-ins gene revealed a TATA-less promoter with significant homology to human c-Jins. Reverse transcriptase primer extension analysis using exon 2 primers identified multiple clustered transcription initiation sites. Their position was confirmed by RNase protection. The same primer extension products were detected in equal abundance from macrophage or nonmacrophage sources of RNA. c-Jins mRNA is acutely down-regulated in primary macrophages by CSF-1, bacterial lipopolysaccharide (LPS), and phorbol myristate acetate (PMA). Each of these agents reduced the abundance of c-fns RNA detectable by primer extension using an exon 3 primer without altering the abundance of presumptive short c-Jins transcripts detected with exon 2 primers. Primer extension analysis with an intron 2 primer detected products at greater abundance in nonmacrophages.Templates detected with the intronic primer were induced in macrophages by LPS, PMA, and CSF-1, suggesting that each of the agents caused a shift from full-length c-Jins mRNA production to production of unspliced, truncated transcripts. The c-Jins promoter functioned constitutively in the RAW264 macrophage cell line, the B-cell line MOPC.31C, and several nonhematopoietic cell lines. Macrophage-specific expression and responsiveness to selective repression by LPS and PMA was achieved by the incorporation of intron 2 into the c-Jins promoter-reporter construct. The results suggest that expression of the c-fins gene in macrophages is controlled by sequences in intron 2 that act by regulating transcription elongation.

The Ewing Sarcoma Protein (EWS) Binds Directly to the Proximal Elements of the Macrophage-Specific Promoter of the CSF-1 Receptor (csf1r) Gene

“…1. The data for the mouse are not completely consistent with previous data based on primer extension (16), probably due to the use of a primer that was too close to the 5Ј end based upon the longest cDNA sequence then available. However, the original data based upon RNase protection (16) was found to be completely consistent with the CAGE pattern shown.…”

“…Luciferase reporter constructs (0.3, 0.5, and 6.7 kb csf1r-luciferase) comprising portions of the murine csf1r promoter in pGL2 (Promega) were as previously described (15,16). Both substitution and deletion mutations of the csf1r promoter were made in 0.5-kb csf1r-luciferase by splice overlap PCR (17).…”

Origins and functions of phagocytes in the embryo

“…PU.1 is expressed at high levels in a macrophage restricted manner. Numerous macrophage promoters have functionally essential PU.1 sites (e.g., c-fms, tartrate-resistant acid phosphatase (TRAP), lysozyme M, macrophage mannose receptor, interleukin 1 (IL-1), F c receptors (F c RI and F c RIIIA), MSR, and CD11b) [150][151][152][153][154][155][156][157][158][159]. In fact, macrophage-specific promoters have an archetypal structure in which purine-rich motifs recognized by PU.1 substitute for conventional TATA box and GC-rich elements found in classic mammalian promoters [158,159].…”

The actions of bacterial DNA on murine macrophages

“…The obvious alternative interpretation of the internalization of the CSF-1R in response to LPS and CpG DNA is that CSF-1 signaling is being specifically switched off. Indeed, down-modulation of the receptor from the cell surface is followed, at least in the case of LPS, by specific repression of c-fms (CSF-1R) mRNA transcription [59] and RAW264 macrophage cells treated with LPS or CpG DNA for a prolonged period deplete both their cell surface and intracellular Golgi-associated pool of CSF-1R [unpublished]. CSF-1 stimulation of macrophages in vivo causes a state of profound T cell non-responsiveness, which has been speculated to be involved in immunosuppression associated with chronic infections [60].…”