CYTOKINE INDUCTION OF PROLIFERATION AND EXPRESSION OF CDC2 AND CYCLIN-A IN FDC-P1 MYELOID HEMATOPOIETIC PROGENITOR CELLS - REGULATION OF UBIQUITOUS AND CELL CYCLE-DEPENDENT HISTONE GENE-TRANSCRIPTION FACTORS

To evaluate transcriptional mechanisms during cytokine induction of my eloid progenitor cell proliferation, we examined the expression and ac tivity of transcription factors that control cell cycle-dependent hist one genes in interleukin-3 (IL-3)-dependent FDC-P1 cells. Histone gene s are transcriptionally upregulated in response to a series of cellula r regulatory signals that mediate competency for cell cycle progressio n at the G1/S-phase transition. We therefore focused on factors that a re functionally related to activity of the principal cell cycle regula tory element of the histone 1-14 promoter: CDC2, cyclin A, as well as RB- and IRF-related proteins. Comparisons were made with activities of ubiquitous transcription factors that influence a broad spectrum of p romoters independent of proliferation or expression of tissue-specific phenotypic properties. Northern blot analysis indicates that cellular levels of cyclin A and CDC2 mRNAs increase when DNA synthesis and H4 gene expression are initiated, supporting involvement in cell cycle pr ogression. Using gel-shift assays, incorporating factor-specific antib ody and oligonucleotide competition controls, we define three sequenti al periods following cytokine stimulation of FDC-P1 cells when selecti ve upregulation of a subset of transcription factors is observed. In t he initial period, the levels of SP1 and HINF-P are moderately elevate d; ATF, AP-1, and HiNF-M/IRF-2 are maximal during the second period; w hile E2F and HiNF-D, which contain cyclin A as a component, predominat e during the third period, coinciding with maximal H4 gene expression and DNA synthesis. Differential regulation of H4 gene transcription fa ctors following growth stimulation is consistent with a principal role of histone gene promoter elements in integrating cues from multiple s ignaling pathways that control cell cycle induction and progression. R egulation of transcription factors controlling histone gene promoter a ctivity within the context of a staged cascade of responsiveness to cy clins and other physiological mediators of proliferation in FDC-P1 cel ls provides a paradigm for experimentally addressing interdependent ce ll cycle and cell growth parameters that are operative in hematopoieti c stem cells. (C) 1995 Wiley-Liss, Inc.