The Short Isoform of NF‐YA Belongs to the Embryonic Stem Cell Transcription Factor Circuitry

Abstract

Totipotency of embryonic stem cells (ESCs) is controlled at the transcriptional level by a handful of transcription factors (TFs) that promote stemness and prevent differentiation. One of the most enriched DNA elements in promoters and enhancers of genes specifically active in ESCs is the CCAAT box, which is recognized by NF-Y, a trimer with histone-like subunits-NF-YB/NF-YC-and the sequence-specific NF-YA. We show that the levels of the short NF-YA isoform-NF-YAs-is high in mouse ESCs (mESCs) and drops after differentiation; a dominant negative mutant affects expression of important stem cells genes, directly and indirectly. Protein transfections of TAT-NF-YAs stimulate growth and compensate for withdrawal of leukemia inhibitory factor (LIF) in cell cultures. Bioinformatic analysis identifies NF-Y sites as highly enriched in genomic loci of stem TFs in ESCs. Specifically, 30%-50% of NANOG peaks have NF-Y sites and indeed NF-Y-binding is required for NANOG association to DNA. These data indicate that NF-Y belongs to the restricted circle of TFs that govern mESCs, and, specifically, that NF-YAs is the active isoform in these cells.

Transcriptional Activation of Human CDCA8 Gene Regulated by Transcription Factor NF-Y in Embryonic Stem Cells and Cancer Cells

“…Sp1 activated the cystathionine-␤-synthase promoter synergistically only with NF-YAL (32). NF-YAS is down-regulated, whereas NF-YAL is up-regulated during differentiation of hESCs (30), mouse ES cells (25,30), and hematopoietic stem cells (26,27). NF-YAS has a crucial role in maintaining stemness by directly activating key stem cell genes in mouse ES cells (25).…”

“…NF-YAS is down-regulated, whereas NF-YAL is up-regulated during differentiation of hESCs (30), mouse ES cells (25,30), and hematopoietic stem cells (26,27). NF-YAS has a crucial role in maintaining stemness by directly activating key stem cell genes in mouse ES cells (25). NF-YAS also plays a central integrating role in the self-renewal of mouse hematopoietic stem cells by activating multiple pathways (27).…”

“…NF-YA has been proved to play an important role in maintaining the stemness of stem cells by activating multiple stem cell genes (25)(26)(27). Thus, we next focused on the role of NF-Y on CDCA8 transcription.…”

Proteasome expression and activity in cancer and cancer stem cells

“…48 In addition, a short isoform of NF-YA regulates the pluripotency program itself in embryonic cells. 49 This prerequisite of high proteasome activity for gene priming is not shared by normal adult tissue stem cells and CSCs which retain a more restricted ability to differentiate to different cells of tissue of origin or to different bulk cancer cells (Figure 3). Interestingly, senescent cells during the aging process display a decreased proteasome activity which may be involved in the association of cancer and aging.…”

Targeting the Y/CCAAT box in cancer: YB-1 (YBX1) or NF-Y?

“…52,81,82 Finally, transfections of recombinant proteins in which NF-YA was linked to a cell-penetrating TAT peptide activate endogenous CCAAT genes but not CCAAT-less units. 83,84 All these features are quite standard for TFs: sequence specificity, modularity of DBD and TA, and synergistic activation with neighboring TFs.…”