Page 26 - Undergraduate Research Opportunities Program Proceedings 2017-18

School of Science
Division of Life Science

Investigation of Novel Mechanisms Underlying Microtubule Organization

Supervisor: QI Robert Zhong / LIFS
Student: LUI Sze Wai / BIOT Course: UROP1000, Summer

The microtubule nucleator γ-tubulin forms new microtubules by assembling into γ-tubulin ring complex (γ-TuRC).
Previously, it is reported that various lysine residues on γ-tubulin can be ubiquitinated under the action of cullin-RING E3
ligases (CRLs). Each CRL contains a cullin protein, and there are 7 members in the cullin family (CUL1, CUL2, CUL3,
CUL4A, CUL4B, CUL5 and CUL7). Through CRLs, the ubiquitinated γ-tubulin is subsequently subjected to proteasome-
mediated degradation. This study centers on identifying the specific CRL(s) involving in γ-tubulin ubiquitination.
Through protein binding assay between γ tubulin and the cullin proteins, we found that CUL1 and CUL4A demonstrated
interactions with γ-tubulin.

Investigating Microtubule Regulation during Cell Proliferation, Migration and Morphogenesis

Supervisor: QI Robert Zhong / LIFS
Student: LUI Sze Wai / BIOT Course: UROP1100, Spring

γ-Tubulin is a crucial component in γ-tubulin ring complex (γ-TuRC) , which is responsible for microtubule nucleation. It
is reported that γ-tubulin can undergo ubiquitination on lysine residues, leading to its destruction by proteasome.
Controlling such process in vivo is essential for regulation of microtubule nucleation. In this study, ubiquitination sites of
γ-tubulin are investigated. Three of the sixteen lysine (K) residues (K48, K113 and K301) in γ-tubulin were mutated to
arginine (R) by QuickChange Site-Directed Mutagenesis. By in vivo ubiquitination assay, three γ-tubulin mutants show
ubiquitination at reduced levels, with K48R and K113R demonstrating a greater reduction effect. Therefore, K48, K113
and K301 could be sites of ubiquitin proteasome-mediated degradation.

Supervisor: QI Robert Zhong / LIFS
Student: SULLIVAN Chantelle Dorothy / BCB Course: UROP1000, Summer

Microtubule nucleation is mainly activated by γ-Tubulin Ring Complex (γTuRC) at Microtubule Organizing Centres (MTOC)
in animal cells. Interestingly, γTuRC binds exclusively to CDK5RAP2 and NEDD1, which are the activating and centrosomal
recruitment factors of γTuRC. CDK5RAP2-bound- and NEDD-bound-γTuRCs display different microtubule nucleation
activity in vitro. However, it is difficult to study the regulation of the nucleation activity of such γTuRC subpopulations in
isolation in cells because of the identical centrosomal localization. Here, the γTuRC-binding domain of CDK5RAP2 was
fused with the plasma-membrane-targeting motif of SRC, for recruiting CDK5RAP2-bound-γTuRCs to plasma membrane.
Cell imaging revealed that chimeric CDK5RAP2 was found in the cytosol, in addition to the plasma membrane. Therefore,
robust cytosolic microtubule nucleation was induced by expressing the plasma-membrane-targeted-CDK5RAP2.

Computational Study of Long Noncoding RNAs in Cancer

Supervisor: WANG Jiguang / LIFS
Student: SHI Hongyu / BCB Course: UROP1100, Fall

Gastric cancer (GC) is one of the leading causes of cancer-related deaths. Previous research devoted great efforts in
revealing genetic variations that may contribute to gastric cancer progression, however, most of them focused on coding
genes. Though many long non-coding RNAs (lncRNA) have been proved to possess diverse regulatory functions in
different biological processes, the role of lncRNAs in GC have not been fully elucidated and it is likely to discovery new
drug targets and biomarkers for GC in lncRNAs. In this UROP project, we aimed to establish a new computational

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