Cholesterol is required for transcriptional repression by BASP1

Abstract

Lipids are present within the cell nucleus, where they engage with factors involved in gene regulation. Cholesterol associates with chromatin in vivo and stimulates nucleosome packing in vitro, but its effects on specific transcriptional responses are not clear. Here, we show that the lipidated Wilms tumor 1 (WT1) transcriptional corepressor, brain acid soluble protein 1 (BASP1), interacts with cholesterol in the cell nucleus through a conserved cholesterol interaction motif. We demonstrate that BASP1 directly recruits cholesterol to the promoter region of WT1 target genes. Mutation of BASP1 to ablate its interaction with cholesterol or the treatment of cells with drugs that block cholesterol biosynthesis inhibits the transcriptional repressor function of BASP1. We find that the BASP1–cholesterol interaction is required for BASP1-dependent chromatin remodeling and the direction of transcription programs that control cell differentiation. Our study uncovers a mechanism for gene-specific targeting of cholesterol where it is required to mediate transcriptional repression.

The BASP1 transcriptional repressor modifies chromatin through lipid-dependent and lipid-independent mechanisms

“…V-K562 and B- K562 cells along with G-K562 cells (expressing BASP1-G2A) were incubated in lipid-free media supplemented with myristic acid alkyne that is utilized by cells as a substrate for N-terminal myristoylation (Wright et al, 2015). Nuclei were then prepared as we described before using a method that avoids contamination with either endoplasmic reticulum or golgi complex (Loats et al, 2021). Using click chemistry, the alkyne-myristoyl moiety was crosslinked to azide-PEG3-biotin which was then detected using a streptavidin-linked fluorophore.…”

“…All samples were prepared in biological triplicates for V-K562, B-K562 and G-K562 cells harvested at 0.7-0.8x10 6 cells /mL (Loats et al, 2021;Toska et al, 2012).…”

“…BASP1 also contains a consensus cholesterol binding motif adjacent to the myristoyl moiety (Epand, 2008). Indeed, both phosphatidylinositol 4,5-bisphosphate (PIP2) and cholesterol are recruited to promoter regions and are required for transcriptional repression by BASP1 (Toska et al, 2012, 2014; Loats et al, 2021). The myristoylation of BASP1 is required for interaction with both PIP2 and cholesterol (Toska et al, 2012; Loats et al, 2021).…”

“…Indeed, both phosphatidylinositol 4,5-bisphosphate (PIP2) and cholesterol are recruited to promoter regions and are required for transcriptional repression by BASP1 (Toska et al, 2012, 2014; Loats et al, 2021). The myristoylation of BASP1 is required for interaction with both PIP2 and cholesterol (Toska et al, 2012; Loats et al, 2021). PIP2 assists in the recruitment of HDAC1 to mediate deacetylation of histone H3K9 and direct transcriptional repression (Toska et al, 2012).…”

Unconventional metabolites in chromatin regulation

“…Further on the notion that cholesterol drives the compaction of nucleosomes, cholesterol was shown to be required for the transcriptional repressor brain acid soluble protein 1 (BASP1)-dependent histone modification and transcriptional repression. As such, BASP1-mediated recruitment of cholesterol might elicit direct effects on the nucleosome that contribute to establishing transcriptionally repressive condensed chromatin at specific genes; yet, further studies are needed to elucidate the exact mechanisms of action [ 98 ].…”