NDP52 activates nuclear myosin VI to enhance RNA polymerase II transcription

Abstract

Myosin VI (MVI) has been found to be overexpressed in ovarian, breast and prostate cancers. Moreover, it has been shown to play a role in regulating cell proliferation and migration, and to interact with RNA Polymerase II (RNAPII). Here, we find that backfolding of MVI regulates its ability to bind DNA and that a putative transcription co-activator NDP52 relieves the auto-inhibition of MVI to enable DNA binding. Additionally, we show that the MVI–NDP52 complex binds RNAPII, which is critical for transcription, and that depletion of NDP52 or MVI reduces steady-state mRNA levels. Lastly, we demonstrate that MVI directly interacts with nuclear receptors to drive expression of target genes, thereby suggesting a link to cell proliferation and migration. Overall, we suggest MVI may function as an auxiliary motor to drive transcription.

Nuclear myosin VI regulates the spatial organization of mammalian transcription initiation

“…Of note, all the parameters quantified showed a large cell-to-cell variation, which may be attributed to the cells not being synchronized. Given the well-established role of myosin VI in transcription (Cook et al, 2018, Fili et al, 2017, Große-Berkenbusch et al, 2020, Vreugde et al, 2006, we assessed whether stimulation of transcription can alter its clustering and thus functional properties.…”

“…Since myosin VI is an ATPase, we then explored whether its nuclear distribution and clustering behaviour was dependent upon its myosin motor activity. To this end, we used the small molecule inhibitor 2,4,6-triiodophenol (TIP) which is known to perturb the motor activity of myosin VI (Heissler et al, 2012) and impact upon transcription (Cook et al, 2018, Fili et al, 2017. TIP treatment disrupted the nuclear organisation of myosin VI ( Figure 1C).…”

“…To determine the specific role of the nuclear population of myosin VI in the spatial organisation of RNAPII, we transfected cells with NLS-tagged truncations of myosin VI, namely NLS-CBD (Cargo-binding domain) and NLS-Motor. Based on in vitro transcription assays (Fili et al, 2017), overexpression of these constructs and their targeting to the nucleus was expected to have a dominant negative impact upon the endogenous nuclear myosin VI by displacing the protein. Indeed, similar to TIP treatment and myosin knockdown, over-expression of either construct disrupted the nuclear distribution of RNAPII, as observed by widefield microscopy (Supplementary Figure 4A and B).…”

“…More recently, they have also been identified within the cell nucleus, where they have roles in transcription, DNA damage and chromosome organisation (de Lanerolle, 2012). 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).…”

“…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).…”