Aberrant chromatin remodeling by retinoic acid receptor alpha fusion proteins assessed at the single-cell level.
Acute promyelocytic leukemia (APL) is characterized by specific chromosomal translocations, which generate fusion proteins such as promyelocytic leukemia (PML)-retinoic acid receptor (RAR)alpha and promyelocytic leukemia zinc finger (PLZF)-RARalpha (X-RARalpha). In this study, we have applied lac operator array systems to study the effects of X-RARalpha versus wild-type RARalpha on large-scale chromatin structure. The targeting of these enhanced cyan fluorescent protein-lac repressor-tagged RARalpha-containing proteins to the gene-amplification chromosomal region by lac operator repeats led to local chromatin condensation, recruitment of nuclear receptor corepressor, and histone deacetylase complex. The addition of retinoic acid (RA) induced large-scale chromatin decondensation in cells expressing RARalpha; however, cells expressing X-RARalpha, especially PML-RARalpha, demonstrated insensitive response to this effect of all-trans retinoic acid (ATRA). Although we did not reveal differences in RA-dependent colocalization of either silencing mediator for retinoid and thyroid or steroid receptor coactivator (SRC)-1 with RARalpha versus X-RARalpha, the hormone-independent association between SRC-1 and X-RARalpha on the array has been identified. Rather, compared with cells expressing RARalpha, fluorescence recovery after photobleaching of live transfected cells, demonstrated decreased mobility of SRC-1 on the X-RARalpha-bound chromatin. Thus, the impaired ability of APL fusion proteins to activate gene transcription in response to ATRA corresponds to their reduced ability to remodel chromatin, which may link to their ability to impair the mobility of key nuclear receptor coregulators.
Department of Medicine, Section of Infectious Disease, Baylor College of Medicine, Houston, TX 77030, USA.
Jihui
J
Qiu
Ying
Y
Huang
Guoqiang
G
Chen
Zhu
Z
Chen
David J
DJ
Tweardy
Shuo
S
Dong
D001426:Bacterial Proteins / Q000378:metabolism; D042002:Chromatin Assembly and Disassembly / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D051548:Histone Acetyltransferases / Q000378:metabolism; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D056985:Nuclear Receptor Co-Repressor 2; D056920:Nuclear Receptor Coactivator 1; D015514:Oncogene Proteins, Fusion / Q000378:metabolism*; D009875:Operator Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology
D001426:Bacterial Proteins; C485182:Cyan Fluorescent Protein; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; C539130:NCOR2 protein, human; D056985:Nuclear Receptor Co-Repressor 2; D015514:Oncogene Proteins, Fusion; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins; D014212:Tretinoin; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; D056920:Nuclear Receptor Coactivator 1