Transcription factor RFX2 is abundant in rat testis and enriched in nuclei of primary spermatocytes where it appears to be required for transcription of the testis‐specific histone H1t gene

Abstract

Previous work in our laboratory revealed upregulated transcription of the testis-specific linker histone H1t gene in pachytene primary spermatocytes during spermatogenesis. Using the H1t X-box as an affinity chromatography probe, we identified Regulatory Factor X2 (RFX2), a member of the RFX family of transcription factors, as a nuclear protein that binds the probe. We also showed that RFX2 activated the H1t promoter in transient expression assays. However, other RFX family members have the same DNA-binding domain and they also may regulate H1t gene expression. Therefore, in this study we examined the distribution of RFX2 and other RFX family members in rat testis germinal cells and in several tissues. Among tissues examined, RFX2 is most abundant in testis. Testis RFX2 is most abundant in spermatocytes where transcription of the H1t gene is upregulated and the steady-state H1t mRNA level is high. RFX2 levels decrease but RFX1 levels increase in early spermatids where H1t gene transcription is downregulated. Antibodies against RFX2 generate a shifted band in electrophoretic mobility shift assays (EMSA) using H1t or testisin X-box DNA probes with nuclear proteins from spermatocytes. These data support the hypothesis that RFX2 expression is upregulated in spermatocytes where it participates in activating transcription of the H1t gene and other testis genes. These data also support the possibility that other RFX family members may bind to the H1t promoter in other testis germinal cell types and in nongerminal cells to downregulate H1t gene transcription.

Germline-specific H1 variants: the “sexy” linker histones

“…RFX2 binds specifically to these elements to activate transcription of the H1t gene in primary spermatocytes and both elements appear required for maximal promoter activity (Grimes et al 2005;Horvath et al 2004;Wolfe et al 2004). In comparison to other RFX proteins, RFX2 is preferentially expressed in testis, being most abundant in spermatocytes where transcription of H1t is upregulated (Horvath et al 2004;Wolfe et al 2006). In spermatids, RFX2 levels decrease whereas RFX1 expression increases (Wolfe et al 2006).…”

“…In comparison to other RFX proteins, RFX2 is preferentially expressed in testis, being most abundant in spermatocytes where transcription of H1t is upregulated (Horvath et al 2004;Wolfe et al 2006). In spermatids, RFX2 levels decrease whereas RFX1 expression increases (Wolfe et al 2006). RFX2 could act as a homodimer (Horvath et al 2004) or, alternatively, could form an heterodimer with RFX4 .…”

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: Intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage‐gated channels, methylation/acetylation, and transcription factors

“…PTBP2 stabilizes the mRNA encoding PGK2 (Xu and Hecht, 2007). Regulatory factor X (RFX2) [ID: T2-354] has been proposed to be a transcriptional regulator factor for H1t [ID: T2-353] Wolfe et al, 2004Wolfe et al, , 2006 . NFY transcription factor, comprised of A [ID: T4-810], B [ID: T4-811], and C [ID: T4-812] subunits, also binds to H1t and interacts with RFX2.…”

Identification and characterization of novel human tissue-specific RFX transcription factors

“…RFX2 [18] and RFX4 [19] are found to be heavily expressed in the testis. RFX4 is also expressed in the brain [20].…”