The Transcription Factor Sp3 Regulates the Expression of a Metastasis-Related Marker of Sarcoma, Actin Filament-Associated Protein 1-Like 1 (AFAP1L1)

Abstract

We previously identified actin filament-associated protein 1-like 1 (AFAP1L1) as a metastasis-predicting marker from the gene-expression profiles of 65 spindle cell sarcomas, and demonstrated the up-regulation of AFAP1L1 expression to be an independent risk factor for distant metastasis in multivariate analyses. Little is known, however, about how the expression of AFAP1L1 is regulated. Luciferase reporter assays showed tandem binding motives of a specificity protein (Sp) located at −85 to −75 relative to the transcriptional start site to be essential to the promoter activity. Overexpression of Sp1 and Sp3 proteins transactivated the proximal AFAP1L1 promoter construct, and electrophoretic mobility shift assays showed that both Sp1 and Sp3 were able to bind to this region in vitro. Chromatin immunoprecipitation experiments, however, revealed that Sp3 is the major factor binding to the proximal promoter region of the AFAP1L1 gene in AFAP1L1- positive cells. Treatment with mithramycin A, an inhibitor of proteins binding to GC-rich regions, prevented Sp3 from binding to the proximal promoter region of AFAP1L1 and decreased its expression in a dose-dependent manner. Finally, knocking down Sp3 using small inhibitory RNA duplex (siRNA) reduced AFAP1L1 expression significantly, which was partially restored by expressing siRNA-resistant Sp3. These findings indicate a novel role for Sp3 in sarcomas as a driver for expression of the metastasis-related gene AFAP1L1.

Sp1 cooperates with Sp3 to upregulate MALAT1 expression in human hepatocellular carcinoma

“…MIT, as a GC-rich region inhibitor, can suppress protein biosynthesis via transcription inhibition (39). It has been shown to inhibit cancer growth by blocking the Sp-family transcription factors from binding to GC-rich regions of gene regulatory elements and is used for the treatment of leukemia and testicular cancer in the US (21,(40)(41)(42)(43)(44)(45). By contrast, MIT has also been shown to exert neuroprotective effects in normal cells and potential as an agent for neurodegenerative diseases (41).…”

Long non‐coding RNA AFAP1‐AS1 is upregulated in a subset of multiple sclerosis patients

“…This lncRNA has been shown to exert oncogenic roles in several types of cancers. 16 Therefore, it is possible that this transcription factor participates in sex-based expression of AFAP1-AS1 as well. 12 LncRNAs have diverse roles in the regulation of genes that alter immune cell functions.…”

“…15 Interestingly, the sexbased differential expression in MS patients was predicted to depend on the transcription factor specificity protein 1, 15 a transcription factor that regulates expression of AFAP1-like 1 protein. 16 Therefore, it is possible that this transcription factor participates in sex-based expression of AFAP1-AS1 as well. As all of the MS patients enrolled in the present study were under IFN-b treatment, it is possible that dysregulation of AFAP-AS1 in patients with MS might be due to IFN-b treatment.…”

A CRISPR/Cas9 Functional Screen Identifies Rare Tumor Suppressors

“…SP family members SP1/3/4 have been implicated as non-oncogenic addiction events in pancreatic cancer xenograft experiments23. Yet, reduced SP3 expression is associated with decreased apoptosis-related caspase activity24 and decreased oncogenicity252627 whereas elevated levels in LS174 modified colon carcinoma cells leads to increased apoptosis and prevents tumor formation in nude mice28.…”