The myeloid lineage‐determining transcription factor PU.1 induces enhancer‐promoter looping that promotes IL‐1β enhancer and messenger RNA production in non‐myeloid melanoma cells

Abstract

The DNA‐binding protein purine rich (PU.1) is a lineage determining transcription factor required for development of myeloid cells such as monocytes/macrophages. PU.1 is regarded as a pioneering transcription factor for macrophage differentiation due to its ability to bind “closed” genomic sites and initiate/maintain “open” chromatin state in macrophage‐restricted response genes. To date, however, precise mechanism of PU.1 in remodeling chromatin is yet to be elucidated. The non‐myeloid melanoma B16.BL6 cells response to the bacterial cell wall component lipopolysaccharide (LPS) and activate the transcription factor NF‐κB, but do not produce cytokines. Ectopic expression of PU.1 rendered these cells express the cytokine interleukin 1‐β (IL1b) in response to LPS. PU.1 induced chromatin remodeling that caused interaction between the IL1b promoter and enhancer (located ~10 kb upstream of the IL1b transcription start site) in non‐activated cells; upon activation, PU.1 recruited NF‐κB to these genomic regions. The N‐terminal domain (1–30) of PU.1 was important for both promoter‐enhancer looping and IL1b eRNA/mRNA production; whereas, the acidic and glutamine rich domains (33–100) were required for eRNA/mRNA production but dispensable for the DNA looping. eRNA production and histone acetylation were required for NF‐κB recruitment and IL1b mRNA expression, but not for the DNA looping. Altogether, this study indicates that PU.1 induces enhancer‐promoter looping that sequentially allows activation‐dependent histone acetylation, recruitment of NF‐κB and production of enhancer RNAs, all of which are required for an optimal IL1b production.Support or Funding InformationThe Natural Sciences and Engineering Research Council of Canada ‐ Discovery Grant (RGPIN‐2018‐05514)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.