Myosin VI regulates gene pairing and transcriptional pause release in T cells

Abstract

Naive CD4 T cells differentiate into several effector lineages, which generate a stronger and more rapid response to previously encountered immunological challenges. Although effector function is a key feature of adaptive immunity, the molecular basis of this process is poorly understood. Here, we investigated the spatiotemporal regulation of cytokine gene expression in resting and restimulated effector T helper 1 (Th1) cells. We found that the Lymphotoxin (LT)/TNF alleles, which encode TNF-α, were closely juxtaposed shortly after T-cell receptor (TCR) engagement, when transcription factors are limiting. Allelic pairing required a nuclear myosin, myosin VI, which is rapidly recruited to the LT/TNF locus upon restimulation. Furthermore, transcription was paused at the TNF locus and other related genes in resting Th1 cells and released in a myosin VI-dependent manner following activation. We propose that homologous pairing and myosin VI-mediated transcriptional pause release account for the rapid and efficient expression of genes induced by an external stimulus.+ T cells have the potential to differentiate into several effector lineages (1), which play distinct roles in adaptive immune responses (2, 3). The polarization process is driven by many well-characterized transcription factors and epigenetic modifications. For instance, following T-cell receptor (TCR) and cytokine-mediated activation, naive CD4 + T cells transcribe low levels of the alternatively expressed genes IFN-γ and IL-4, IL-5, and IL-13, irrespective of their ultimate effector lineage fate (4). During differentiation, however, contrasting activation patterns are established: T helper 1 (Th1) cells exclusively express the signature cytokine interferon-gamma (IFN-γ) in a T-bet-dependent manner, whereas Th2 cells exclusively express IL-4, IL-5, and IL-13 in a Gata3-dependent manner. These changes in transcriptional activity have been demonstrated by the appearance of DNase I hypersensitive sites, as well as by changes in histone acetylation and DNA methylation patterns (5-8). Furthermore, recent work has demonstrated that interchromosomal associations between cytokine genes play an important role in the differentiation process (9, 10). Overall, a vast array of transcription factors, epigenetic modifications, and long-range interactions are needed to establish the identity of effector Th cells. An important aspect of effector T-cell function is the rapid and efficient induction of cytokine gene expression upon antigen encounter. However, the precise spatial and temporal aspects of effector T-cell transcriptional activation are still largely unknown.A fundamental feature of genome regulation is the spatial organization of genes into chromosomal territories. Although chromosomes occupy distinct territories in the nucleus, their location is cell type-specific and may change upon cellular activation. Notably, cell activation has been shown to promote extensive intermingling among chromosomal territories (11,12). In addition, the position of individual gene...

Nuclear myosin VI regulates the spatial organization of mammalian transcription initiation

“…This approach could enable enhanced RNAPII binding to initiate transcription and facilitate rapid recycling of RNAPII to drive higher expression levels. Such a mechanism would also fit with the observation that myosin VI functions in gene pairing (Zorca et al, 2015). We have previously shown that myosin VI interacts with RNAPII through actin (Fili et al, 2017), present within the RNAPII complex.…”

“…The minus-end directed myosin, Myosin VI ( Figure 1A), has been shown to bind DNA through its cargo binding domain (CBD) and couple itself to RNAPII in an actin-dependent manner through the motor domain (Fili et al, 2017). It has been revealed that the ability of myosin VI to bind DNA and its ATPase activity are both critical for transcription in vitro (Cook et al, 2018, Fili et al, 2017, and myosin VI can function in gene pairing (Zorca et al, 2015). Recently, myosin VI has been shown to actively undergo directed motion in the nucleus in response to transcription stimulation (Große-Berkenbusch et al, 2020).…”

Myosin VI Contains a Compact Structural Motif that Binds to Ubiquitin Chains

“…A recent study suggests that the need for heterotypic chains may be derived from poor binding to mammalian proteasome of ubiquitin chains that are linked exclusively by K11 (Grice et al, 2015). Notably, a few reports suggest a nuclear function for myosin VI (Vreugde et al, 2006; Zorca et al, 2015). In this subcellular compartment, myosin VI may interact with proteins modified by K11-linked chains to regulate transcription and viral infection.…”

Functions and properties of nuclear lncRNAs—from systematically mapping the interactomes of lncRNAs

“…The first study showed that RNA constitutes a significant fraction of chromatin date back over 50 years ago [41,42]. Later studies provide evidence to support the idea that a nuclear matrix is made of insoluble proteins and RNA in an interphase nucleus [43]. Treatment of RNase A leads to clumping of chromatin onto nuclear lamina and nucleolus [44,45], indicating an indispensable role of RNA in the nuclear architecture.…”