Involvement of PIP2 in RNA Polymerase I transcription

Abstract

SummaryRNA polymerase I (Pol I) transcription is essential for the cell cycle, growth and protein synthesis in eukaryotes. In the present study, we found that phosphatidylinositol 4,5-bisphosphate (PIP2) is a part of the protein complex on the active ribosomal promoter during transcription. PIP2 makes a complex with Pol I and the Pol I transcription factor UBF in the nucleolus. PIP2 depletion reduces Pol I transcription, which can be rescued by the addition of exogenous PIP2. In addition, PIP2 also binds directly to the pre-rRNA processing factor fibrillarin (Fib), and co-localizes with nascent transcripts in the nucleolus. PIP2 binding to UBF and Fib modulates their binding to DNA and RNA, respectively. In conclusion, PIP2 interacts with a subset of Pol I transcription machinery, and promotes Pol I transcription.

Phosphatidylinositol-4-phosphate 5-Kinase 1α Modulates Ribosomal RNA Gene Silencing through Its Interaction with Histone H3 Lysine 9 Trimethylation and Heterochromatin Protein HP1-α

“…2A, panel c). Previously, the nuclear PIP 2 had been shown to be regulated by cell cycle stages (33) and to interact with Pol I and upstream binding factor in the nucleolar cap region (8). Interestingly, our study revealed an enhanced accumulation of PIP5K in the nucleolar cap region upon G 1 /S arrest in multiple cell types (Figs.…”

“…Further observations showed that PIP 2 can regulate the interaction of the chromatin remodeling complex BRG1-or HRBM-associated factors (BAF) with the nuclear matrix (7). Recent evidence also has identified PIP 2 in the nucleolus interacting with Pol I and upstream binding factor, implicating a possible role in Pol I transcription by interacting with pre-rRNA production and processing machineries (8). Although there have been some reports on the role of PIP 2 in the nucleus, only a few studies have documented spatial and functional characterization of PIP5K in the nucleus.…”

Inositol phosphate pathway controls transcription of telomeric expression sites in trypanosomes

“…A general model that embraces knowledge from other systems (19,20,22) is that certain IP metabolites may specifically bind to proteins that have roles in telomeric silencing and affect their interactions with other proteins and/or their functions, e.g., histone modification and chromatin remodeling. The ultimate consequence of the derepression is that the chromatin at multiple ESs is permissive for the elongation of transcription by Pol I through the VSG genes.…”

“…The inositol phosphate (IP) pathway regulates multiple cellular processes in eukaryotes including chromatin remodeling and gene expression (18)(19)(20)(21). Soluble IPs or lipid-conjugated phosphatidylinositols (PIs) occur in various cellular compartments, where they act as cofactors in the regulation of the functions or interactions of proteins (22,23).…”

DNA-Lipids-Me2+ Complexes Structure and their Possible Functions in a Cell

“…Not all pre-pores reach the nuclear envelope and form nuclear pores during chromosome decondensation in prophase. Pre-pores remaining inside of the nucleus form aggregates, which may be the transcription factories discovered not so long ago in the nuclei [43]. These structures are very similar to pre-pore aggregates and are transcriptional active.…”