The dynein adaptor Hook2 plays essential roles in mitotic progression and cytokinesis
Dwivedi, D., Kumari, A., Rathi, S., Mylavarapu, S., & Sharma, M. (2019). The dynein adaptor Hook2 plays essential roles in mitotic progression and cytokinesis. The Journal of cell biology, 218(3), 871–894. https://doi.org/10.1083/jcb.201804183
Journal club, teaching others about science and new innovations are some of the things I love. However, most of the peer reviewed articles are very dense and many times even a small bit of help understanding them can go a long way. This week we will be taking a look at an important paper in cytokinesis. Often, I re-read these papers with others and try to formulate a method to help everyone understand them. I am not the original author of this paper, and I hope I have given proper credit to the authors. Research takes time, and every time you read a paper like this one please understand, it may represent years of research. Hopefully, the link to the original paper works, if not, copy paste the title.
1. What is a dynein-adapter? is an essential cellular motor that drives the movement of diverse cargos along the microtubule cytoskeleton, including organelles, vesicles and RNAs. Dynein adopts an inactive conformation when not attached to a cargo, and motility is activated when dynein assembles with dynactin and a cargo adaptor.
2. Where does Hook2 localize and what is known about its functions? Hook2 is a dynein-adapter it localizes to the centrosome through all phases of the cell cycle, the C‐terminal domain of hook2 directly binds to centriolin/CEP110, the expression of the C‐terminal domain of centriolin/CEP110 alters the distribution of endogenous hook2 and mis localized wild‐type or mutant hook2 proteins perturb endogenous centrosomal and pericentrosomal proteins in cultured mammalian cells. Hook2 is a linker required for assembly of dynein–dynactin complex
3. What is the hypothesis of the paper? Hook2 mediates
assembly of the dynein–dynactin complex and regulates mitotic progression and cytokinesis. Hook2 depletion results in cytokinesis failure. Hook2 depletion results in cytokinesis failure. Hook2 function is the linker between dynein-dynactin is conserved across evolution.
4. Briefly describe how the hypothesis was tested. HEK 293 cells and HeLa cells, zebrafish, p150 glued cells, siRNA treated cells, mouse embryos. Zebra fish have two Hook paralogs, one is 57% identical and 72% similar to human homolog Hook2.
5. Do these results match your own hypothesis? Why or why not? Not answered.
Homolog: a gene related to a second gene by decent of a common ancestorial DNA sequences
(MBP) maltose-binding protein
NE: Nuclear envelope
Nucleation is the first step in the formation of either a new thermodynamic phase or a new structure via self-assembly or self-organization. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears.
(EV) Empty Vector: One transfection control is an empty vector control; specifically, the plasmid without the independent variable. … The empty vector control allows you to examine if the transfection reagents or the transfection process itself has any cytotoxic effects on the target cells (EV)
Multinucleated cell Figure 7. Imagine a cell that completed mitosis but never underwent cytokinesis. In some cases, a cell may divide its genetic material and grow in size but fail to undergo cytokinesis. This results in larger cells with more than one nucleus. Usually this is an unwanted aberration and can be a sign of cancerous cells.
Dynein is a minus-end–directed microtubule motor important for mitotic spindle positioning.
Kinesins and dyneins have similarities, but an important difference is that most kinesins travel toward the plus end of the microtubule that they are on (i.e., away from the center of the cell), while dyneins travel toward the minus end of the microtubule (towards the center of the cell).
Dyneins are large molecular motors that hydrolyze ATP to generate a minus-end-directed force along microtubules. Each dynein consists of one to three dynein heavy chains (HCs), which encompass the ATPase activity, complexed to intermediate (IC), light intermediate (LIC), and light chains (LC).
Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information.
Mitosis: In cell biology, mitosis is a part of the cell cycle, in which, replicated chromosomes are separated into two new nuclei. Cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained Mitosis is the process in which the nucleus of a eukaryotic cell divides. During this process, sister chromatids separate from each other and move to opposite poles of the cell. This happens in four phases, called prophase, metaphase, anaphase, and telophase. Mitosis is important for three main reasons: development and growth cell replacement and asexual reproduction
G2 Phase The last part of interphase is called the G2 phase. The cell has grown, DNA has been replicated, and now the cell is almost ready to divide. This last stage is all about prepping the cell for mitosis or meiosis. During G2, the cell has to grow some more and produce any molecules it still needs to divide.
During late in G2 phase (so after DNA replication) so the cell is preparing for mitosis G2
Hook2-depleted cells have reduced astral microtubules and spindle positioning defects. Besides the centrosome, Hook2 localizes to and recruit’s dynactin and dynein to the central spindle. Hook2 depletion results in cytokinesis failure.
Hook2 is required for dynein–dynactin association upon entry into mitosis Previous studies have shown that dynein regulates multiple stages of the cell cycle, including centrosome anchoring to the NE, chromosome alignment, spindle pole focusing, spindle positioning, and spindle assembly checkpoint inactivation.
Figure 1. Hook2 acts as a dynein-dynactin linker
Figure 2. Hook2 is required for dynein association with dynactin during mitosis
Figure 3. Hook2 regulates anchoring of the centrosomes to the NE Nuclear Envelope
Figure 4. Hook2 is required for p150glued localization to the NE during the late G2 phase by regulating CENP-F-dynein interaction
Figure 5. Hook2 depletion results in mitotic progression defects
Figure 6. Hook2 regulates MT nucleation at the centrosome
Figure 7. binucleated HeLa cells, yellow asterisks
Figure 8. central spindles Hook2 localized to the central spindles and promotes recruitment of dynein and dynactin
Figure9 Hook2 is required for p150glued and MKLP1 interaction during cytokinesis