TCL1A, a novel transcription factor and a coregulator of nuclear factor kB p65: Single nucleotide polymorphism and estrogen dependence^s

T-cell leukemia 1A (TCL1A) single-nucleotide polymorphisms (SNPs) have been associated with aromatase inhibitor-induced musculoskeletal adverse events. We previously demonstrated that TCL1A is inducible by estradiol (E₂) and plays a critical role in the regulation of cytokines, chemokines, and Toll-like receptors in a TCL1A SNP genotype and estrogen-dependent fashion. Furthermore, TCLIA SNP-dependent expression phenotypes can be “reversed” by exposure to selective estrogen receptor modulators such as 4-hydroxytamoxifen (4OH-TAM). The present study was designed to comprehensively characterize the role of TCL1A in transcriptional regulation across the genome by performing RNA sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) assays with lymphoblastoid cell lines. RNA-seq identified 357 genes that were regulated in a TCL1A SNP- and E₂-dependent fashion with expression patterns that were 4OH-TAM reversible. ChIP-seq for the same cells identified 57 TCL1A binding sites that could be regulated by E₂ in a SNP-dependent fashion. Even more striking, nuclear factor-kB (NF-kB) p65 bound to those same DNA regions. In summary, TCL1A is a novel transcription factor with expression that is regulated in a SNP- and E₂-dependent fashion—a pattern of expression that can be reversed by 4OH-TAM. Integrated RNA-seq and ChIP-seq results suggest that TCL1A also acts as a transcriptional coregulator with NF-kB p65, an important immune system transcription factor.