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Actin and the ARP 2/3 complex in the nucleus
Němcová, Barbora ; Bellinvia, Erica (advisor) ; Hála, Michal (referee)
The eukaryotic actin cytoskeleton is required for numerous cellular processes, including cell shape, development and movement, gene expression and signal transduction, and response to biotic and abiotic stress. Actin constitutes a wide family of proteins that are major components of the cytoskeleton. Actin is one of the most abundant proteins in living organisms. Actin has essential functions both in the cytoplasm and in the nucleus, where it has been linked to key nuclear processes. Recent studies have shown that actin is actively transported from the cytoplasm to the nucleus, where it regulates transcriptional aktivity, regulates RNA polymerases, is involved in chromatin remodeling and repair damaged DNA. The presence of typical actin filaments in the nucleus has not been demonstrated directly.but nuclear actin occurs in many forms such as actin rods, short actin polymers, actin monomers, or actin complexes with profilin or cofilin. Most eukaryotic cells also contain at least eleven actin-related proteins (ARPs). Although many ARPs are cytoskeletal, recent biochemical and genetic work has demonstrated that some ARPs function largely or entirely in the nucleus. Nuclear ARPs are recognized as novel key regulators of genome function, and affect not only the remodeling of chromatin but also the...
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Functions of actin and myosin 1c in the cell nucleus and in the cytoplasm
Kalendová, Alžběta ; Hozák, Pavel (advisor) ; Binarová, Pavla (referee) ; Forstová, Jitka (referee)
Human MYO1C gene encodes three myosin 1c (Myo1c) isoforms which differ only at their N-ends. Interestingly, all three isoforms localize to the nucleus and also to the cytoplasm, where they are anchored to the plasma membrane by the interaction with phosphatidyl inositol-4,5-bisphosphate (PIP2). However, studies reporting functional involvement of these isoforms are inconsistent. While the shortest isoform C (Myo1c-isoC) has been implicated exclusively in the cytoplasmic processes, the longer isoform B (termed the nuclear myosin 1, NM1) has been employed in the nuclear and processes, such as DNA transcription and rRNA maturation. Similarly, the longest isoform A (Myo1c-isoA) exerts its functions in the nucleus solely. To complete the information on the cellular functions of Myo1c isoforms, we searched for the cytoplasmic functions of NM1 and nuclear functions of Myo1c-isoC. In mouse, only two isoforms (NM1 and Myo1c-isoC) are expressed. We prepared the knock-out mouse (KO) which lacks specifically NM1 while retaining Myo1c-isoC unchanged. Surprisingly, this manifested in no phenotype observed. Since we demonstrated that even Myo1c-isoC acts in the transcription in the similar manner as NM1, it suggests that Myo1c- isoC functionally overlap with NM1 in the nuclear functions. Besides its localization...
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