The Nuclear Abundance of Transcription Factors Sp1 and Sp3 Depends on Biotin in Jurkat Cells

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Abstract
Biotin affects gene expression in mammals; however, the signaling pathways leading to biotin-dependent transcriptional activation and inactivation of genes are largely unknown. Members of the Sp/Krüppel-like factor family of transcription factors (e.g., the ubiquitous Sp1 and Sp3) play important roles in the expression of numerous mammalian genes. We tested the hypothesis that the nuclear abundance of Sp1 and Sp3 depends on biotin in human T cells (Jurkat cells) mediating biotin-dependent gene expression. Jurkat cells were cultured in biotin-deficient (0.025 nmol/L) and biotin-supplemented (10 nmol/L) media for 5 wk prior to transcription factor analysis. The association of Sp1 and Sp3 with DNA-binding sites (GC box and CACCC box) was 76–149% greater in nuclear extracts from biotin-supplemented cells compared with biotin-deficient cells, as determined by electrophoretic mobility shift assays. The increased DNA-binding activity observed in biotin-supplemented cells was caused by increased transcription of genes encoding Sp1 and Sp3, as shown by mRNA levels and reporter-gene activities; increased transcription of Sp1 and Sp3 genes was associated with the increased abundance of Sp1 and Sp3 protein in nuclei. Notwithstanding the important role for phosphorylation of Sp1 and Sp3 in regulating DNA-binding activity, the present study suggests that the effects of biotin on phosphorylation of Sp1 and Sp3 are minor. The increased nuclear abundance of Sp1 and Sp3 in biotin-supplemented cells was associated with increased transcriptional activity of 5′-flanking regions in Sp1/Sp3-dependent genes in reporter-gene assays. This study provides evidence that some effects of biotin on gene expression might be mediated by the nuclear abundance of Sp1 and Sp3.