Tag Archives: cell biology

Congratulations to Yansong Miao on his new paper!

Yansong Miao‘s new paper is out now at The Proceedings of the National Academy of Sciences.  Congratulations to Yansong on his great work!  The abstract is below.  The PDF can be downloaded from PNAS here.

Cell-cycle regulation of formin-mediated actin cable assembly. Miao Y, Wong CC, Mennella V, Michelot A, Agard DA, Holt LJ, Yates JR 3rd, Drubin DG. Proc Natl Acad Sci U S A. 2013 Nov 19;110(47):E4446-E4455. Epub 2013 Oct 16.  PMID: 24133141


Assembly of appropriately oriented actin cables nucleated by formin proteins is necessary for many biological processes in diverse eukaryotes. However, compared with knowledge of how nucleation of dendritic actin filament arrays by the actin-related protein-2/3 complex is regulated, the in vivo regulatory mechanisms for actin cable formation are less clear. To gain insights into mechanisms for regulating actin cable assembly, we reconstituted the assembly process in vitro by introducing microspheres functionalized with the C terminus of the budding yeast formin Bni1 into extracts prepared from yeast cells at different cell-cycle stages. EM studies showed that unbranched actin filament bundles were reconstituted successfully in the yeast extracts. Only extracts enriched in the mitotic cyclin Clb2 were competent for actin cable assembly, and cyclin-dependent kinase 1 activity was indispensible. Cyclin-dependent kinase 1 activity also was found to regulate cable assembly in vivo. Here we present evidence that formin cell-cycle regulation is conserved in vertebrates. The use of the cable-reconstitution system to test roles for the key actin-binding proteins tropomyosin, capping protein, and cofilin provided important insights into assembly regulation. Furthermore, using mass spectrometry, we identified components of the actin cables formed in yeast extracts, providing the basis for comprehensive understanding of cable assembly and regulation.

Miao 2013 PNAS Figure 2

Average intensity projections along the z-axis of WT cells stained with Alexa-568 phalloidin to label actin filaments and expressing GFP-Tub1 as a cell-cycle stage indicator, obtained using 3D SIM microscopy.

Journal Club on Monday, August 6

For Journal Club on August 6, Eric Lewellyn presented the following paper:

Actin filament severing by cofilin dismantles actin patches and produces mother filaments for new patches. Chen Q, Pollard TD. Curr Biol. 2013 Jul 8;23(13):1154-62. PMID: 23727096.

Chen & Pollard Curr Biol 2013

“Sever, diffuse and trigger” model for actin filament turnover in actin patches. The 7 steps (numbers next to the arrows) are (1) clathrin coated pits bind adaptor proteins End4p and Pan1p, (2) short, diffusing actin filaments bind to End4p and Pan1p associated with coated pits, and (3) Arp2/3 complex interacts with these mother filaments and nucleation promoting factors to (4) initiate branching nucleation of actin filaments that promote elongation of the endocytic tubule. (5) After abscission of the vesicle, (6) cofilin severs actin filaments to generate a pool of short, diffusing actin filaments, some of which return to the cycle at step 2.

Journal Club on Monday, July 22

For Journal Club on July 22, Connie Peng presented the following paper:

Mps1 and Ipl1/Aurora B act sequentially to correctly orient chromosomes on the meiotic spindle of budding yeast. Meyer RE, Kim S, Obeso D, Straight PD, Winey M, Dawson DS. Science. 2013 Mar 1;339(6123):1071-4. PMID: 23371552

Meyer Science 2013

Meyer Science 2013


Journal Club on Monday, June 3

For our Journal Club on June 3, Daphné Dambournet presented the following paper:

Divergent modes for cargo-mediated control of clathrin-coated pit dynamics. Soohoo AL, Puthenveedu MA. Mol Biol Cell. 2013 Jun;24(11):1725-34. PMID: 23536704.

Soohoo MBoC 2013

Model for divergent modes of cargo-mediated control of endocytosis by signaling receptors.

Microtubules and Mitosis Journal Club on Thursday, May 23

For Microtubules and Mitosis Journal Club on April 25, members of the Drubin/Barnes Lab, Eva Nogales Lab, and Ahmet Yildiz Lab discussed the following paper, selected by Anthony Cormier:

Tension sensing by Aurora B kinase is independent of survivin-based centromere localization. Campbell CS, Desai A. Nature. 2013 May 2;497(7447):118-21. PMID: 23604256.

Campbell Nature 2013

Model for mechanism of chromosome biorientation.

Journal Club on Monday, May 13

For our Journal Club on May 13, Christa Cortesio presented the following paper:

ER-to-plasma membrane tethering proteins regulate cell signaling and ER morphology. Manford AG, Stefan CJ, Yuan HL, Macgurn JA, Emr SD. Dev Cell. 2012 Dec 11;23(6):1129-40. PMID: 23237950.

Manford et al Dev Cell 2012

Localization of the ER marker Sec61-GFP in wild-type and Δtether cells (ist2Δ, scs2/22Δ, and tcb1/2/3Δ).

Journal Club on Monday, April 29

For our Journal Club on April 29, Sun Hae Hong presented the following paper:

The molecular basis for the endocytosis of small R-SNAREs by the clathrin adaptor CALM. Miller SE, Sahlender DA, Graham SC, Höning S, Robinson MS, Peden AA, Owen DJ. Cell. 2011 Nov 23;147(5):1118-31. PMID: 22118466

Schematic representation of the model of VAMP8 trafficking from the plasma membrane.

Microtubules and Mitosis Journal Club on Thursday, April 25

For our new Microtubules and Mitosis Journal Club on April 25, members of the Drubin/Barnes Lab, Eva Nogales Lab, and Ahmet Yildiz Lab discussed the following paper, selected by Nate Krefman:

Estimating the microtubule GTP cap size in vivo. Seetapun D, Castle BT, McIntyre AJ, Tran PT, Odde DJ. Curr Biol. 2012 Sep 25;22(18):1681-7. PMID: 22902755

Example EB1 comet from an EB1-EGFP LLCPK1 cell and the corresponding fluorescence intensity (FI) linescan, blue line.

Journal Club on Thursday, April 18

For our Journal Club on April 18, Akemi Kunibe presented the following paper:

Endoplasmic reticulum-associated mitochondria-cortex tether functions in the distribution and inheritance of mitochondria. Lackner LL, Ping H, Graef M, Murley A, Nunnari J.  Proc Natl Acad Sci U S A. 2013 Feb 5;110(6):E458-67. PMID: 23341591.

The ER is a component of the Num1 mitochondria–cell cortex tether.

Journal Club on Monday, March 17

For our Journal Club on March 17, Rebecca Lu will present the following paper:

Robust polarity establishment occurs via an endocytosis-based cortical corralling mechanism. Jose M, Tollis S, Nair D, Sibarita JB, McCusker D. J Cell Biol. 2013 Feb 18;200(4):407-18. PMID: 23401000

Schematics illustrating the mathematical model. Shown are the Cdc42 autoamplification module (A), the complete endocytosis module (B), the exocytosis module (C), and a legend for graphics (D).