Actin, actin-binding proteins, and actin-related proteins in the nucleus

Abstract

Extensive research in the past decade has significantly broadened our view about the role actin plays in the life of the cell and added novel aspects to actin research. One of these new aspects is the discovery of the existence of nuclear actin which became evident only recently. Nuclear activities including transcriptional activation in the case of all three RNA polymerases, editing and nuclear export of mRNAs, and chromatin remodeling all depend on actin. It also became clear that there is a fine-tuned equilibrium between cytoplasmic and nuclear actin pools and that this balance is ensured by an export-import system dedicated to actin. After over half a century of research on conventional actin and its organizing partners in the cytoplasm, it was also an unexpected finding that the nucleus contains more than 30 actin-binding proteins and new classes of actin-related proteins which are not able to form filaments but had evolved nuclear-specific functions. The actin-binding and actin-related proteins in the nucleus have been linked to RNA transcription and processing, nuclear transport, and chromatin remodeling. In this paper, we attempt to provide an overview of the wide range of information that is now available about actin, actin-binding, and actin-related proteins in the nucleus.

β-Actin regulates interleukin 6-induced p21 transcription by interacting with the Rpb5 and Rpb7 subunits of RNA polymerase II

“…Accumulating data have revealed that actin also exists in the nucleus (Pederson & Aebi 2002;Bettinger et al 2004;Kristo et al 2016) and is required for transcription and other processes in the nucleus (Miralles & Visa 2006;Percipalle & Visa 2006;Falahzadeh et al 2015). Previous studies showed that actin interacts with Pol I, II and III and plays a key role in basal transcription Hu et al 2004;Philimonenko et al 2004;Ye et al 2008).…”

Functions of nuclear actin-binding proteins in human cancer (Review)

“…Since the existence of nuclear actin was confirmed, subsequent studies also established the presence of ABPs in the nucleus (12,14,15). The very first nuclear ABP was reported as early as 1987, henceforth, the rest of the ABP family in the nucleus has come to light comprising of proflilin, anillin, flightless I (Fli I), filamin α (FLNα), α-actinins, myosins, gelsolin and ezrin-radixin-moesin proteins (12,13,16,17). Although these ABPs are primarily in the cytoplasm, they can translocate into the nucleus under certain circumstances, for example, extracellular stimuli (stress), hormone stimulation and intracellular signaling (16).…”

“…Studies in the recent decades provide a plethora of evidence that has broadened our horizon on the functions of nuclear actin and nuclear ABPs in the eukaryotic cell life (12)(13)(14). Since the existence of nuclear actin was confirmed, subsequent studies also established the presence of ABPs in the nucleus (12,14,15).…”

“…Nuclear ABPs are closely associated to nuclear actin and implicated in various nuclear activities. ABPs promote actin filament nucleation or sequestering, manipulate nuclear actin dynamics and determine the ratio of nuclear to cytoplasmic actin (13). Therefore, ABPs directly or indirectly associate with chromatin remodeling, DNA replication, transcription, DNA repair, nucleocytoplasmic transport and maintenance of nuclear structure integrity (12,13,21).…”

In focus in Vienna: the cell nucleus

“…Structural determinants are of crucial importance for nuclear organization. Current knowledge on nuclear actin is reviewed in "Actin, actin-binding proteins, and actin-related proteins in the nucleus" (Kristó et al 2016), whereas Harata and coworkers present data on the interaction of nuclear F-actin and β-catenin (Yamazaki et al 2016). Aspects of the growth of another structural entity, the nuclear lamina, were presented by Zhironkina et al (2016).…”