Cell Biology Week 1~ QUT LQB485/ LQB 485

Flash cards for LQB485 Cell Biology week 1

Nucleus - Function

Functions:

• house and protect Genetic material

• synthesis of mRNA

• Ribosome production

• Cell division

• Prevents incorrect translation

Nucleus Structure

Structures:

• Nuclear membrane ~ with pores

• Nuclear lamina

• Nucleoplasm

  • DNA

  • Proteins

  • RNA

  • Other molecules

• Nucleolus / Nucleoli

Polynucleated cells - Origin

Originate from:

• Fusion of multiple cells

• Flawed cell division

What are polynucleated cells

Definition:

A eukaryotic cell that has more than one nuclei

what are anucleate cells

Definition:

Cells that lack a nucleus the cell is incapable of cell division

Nuclear Membrane - Structures

Structures:

• Inner and outer membrane

  • Outer membrane is continuous with ER

• nuclear pore complex

Nuclear pore complex (NPC’s) - Structure

Structure:

Internal part = Nuclear basket

external part = Nuclear filaments

Internal part = complex of 50 - 100 different proteins

Nuclear pore function

Function:

• Nucleocytoplasmic transport

• Small molecules pass rapidly through by passive diffusion

• Larger macromolecule are selectively transported

Nuclear envelope during the cell cycle

Stages:

• Nuclear envelope breaks down in late prophase

• Nuclear envelope reassembles in late telophase

How the nuclear envelope reassembles in late telophase

Process:

• ER membrane reassembles around a compact chromosome masses

• Reassembly involves addition of ~ 10,000 nuclear pores

• New nuclear envelope wraps tightly around chromosomes

Nuclear pore complexes during the cell cycle

Process:

• Nuclear volume and nuclear pore complexes almost double during interphase

• As membrane breaks down NPC proteins are taken into the ER. process is reversed when membrane reforms

Laminopathies

What:

Laminopathies are a group of rare genetic mutations in nuclear lamina coding genes.

Function of LMNA gene

Function:

LMNA gene is responsible for the production of the proteins lamin A and lamin C through alternative splicing which are major components of the nuclear lamina.

Nuclear lamina function + what it can complex with

Function:

• maintaining nuclear shape

• anchors nuclear pores

• role in chromatin regulation - impacts DNA replication, repair ect.

Complexes with:

• integral proteins on inner nuclear membrane

• transcriptional regulators

• histones and chromatin modifiers

3 main laminopathic diseases being focused

Laminopathic diseases:

• Huthcinson-Gilford progeria syndrome (HGPS)

• Emery-Dreifuss muscular dystrophy (EDMD)

• Restrictive dermopathy

Huchinson-Gilford progeria syndrome (HGPS)

Symptoms:

Premature and accelerated ageing.

Caused by:

Mutations in the LMNA gene

• 70% caused by a C > T mutation at 1824

• ~10% caused by G > A mutation at 1821

Mutation does not allow cleavage not allowing mature functional lamin A to be produced

results in progerin buildup which implants into the inner nuclear membrane causing structural insability

Restrictive Dermopathy

Symptoms:

• more sever laminopathy tight and easily eroded skin and contracture of joints.

• Delayed growth, premature birth, reduced movement in utero and death soon after birth

Caused by:

• Lamin A gene - rarely

• ZMPSTE24 gene - more common

HGPS and restrictive dermatopathy treatments

Treatment:

• Lonafarnib inhibits farnesyltransferase which blocks farnesylation preventing build up of progerin

• This does not stop disease progression but it does slow it down

Emerry-Dreifuss muscular dystrophy

Symptoms:

• contracture of major tendons

• skeletal muscle wasting

Caused by

• LMNA gene - 45% of cases

• inner membrane protein eminin (EMD)

• 45% unidentified causes

Emerin (EMD) function + expression

Expressed:

• commonly expressed in the inner nuclear membrane

Function:

• binds lamin A

• chromatin structure

• nuclear structure

• gene expression