Psip1, also known as LEDGF, is a chromatin protein associated with the transcriptional elongation complex. It has histone chaperone activity and is involved in recruiting RNA processing and DNA repair factors to transcription sites, playing a crucial role in maintaining genome integrity. It also has implications in transcriptional regulation, alternative splicing, and is associated with various biological pathways and diseases [1,3,4,5]. Genetic models, such as gene knockout mouse models, are valuable for studying its functions.

In gene-depleted human and mouse cell lines, the absence of Psip1 leads to an accumulation of R-loops and DNA damage at gene promoters, causing local transcriptional arrest and transcription-replication conflict. This suggests that Psip1 reduces R-loops at transcription sites to maintain genome integrity [1]. In T-ALL mouse models, loss of Psip1 accelerates T-ALL initiation correlated with reduced H3K27me3 binding, while in T-ALL cell lines, its loss impairs cell proliferation, indicating a dual role in T-ALL [2].

In conclusion, Psip1 is essential for maintaining genome integrity by reducing R-loops at transcription sites. Its dual role in T-ALL, as revealed through mouse models, provides insights into its functions in this disease. These findings enhance our understanding of Psip1's biological functions and its potential as a therapeutic target in related diseases.