1. I principali compartimenti intracellulari di una cellula animale
15.1

6. Sequenze e Zone SEGNALE
dirigono le proteine al corretto indirizzo cellulare

11. THE NUCLEUS Euchromatin (“normal”)
05_19_Interphase.jpg
CHROMATIN
Euchromatin (“normal”)
Heterochromatin (highly condensed, ~10%)

12. Nucleus Structure About 10% of the cell volume
Contains DNA - condensed and organized with proteins as chromatin
Nuclear matrix – protein-containing fibrillar network
Nucleolus - (pl. nucleoli) –rRNA synthesis, ribosome assembly
Surrounded by nuclear envelope

13. Active chromatin (euchromatin) appear lighter
Inactive chromatin (heterochromatin) is darker and located near periphery of nucleus
Nucleolus
a granular region
site of ribosome assembly
Interphase nucleus

15. Nuclear envelope (INVOLUCRO NUCLEARE):
2 lipid bilayer membranes, nm apart
the outer membrane is continuous with endoplasmic reticulum
a denser layer of intermediate filaments, the nuclear lamina, is within the inner membrane
composed of lamin proteins
provides structure to nucleus, heterochromatin binding site

16. 12 year boy with progeria
Defect in lamin A gene results in progeria – premature aging

20. Il complesso del poro nucleare

21. Nuclear Pores: ~3000/nucleus how the cell moves molecules into and out of the nucleus.
At the pore, the inner and outer membranes come together forming an opening.
Opening is lined with proteins: nuclear pore complex
at least 30 different nucleoporin proteins, in octagonal symmetry ( total proteins)
Including cytoplasmic filaments, extending to the cytoplasm

23. The role of nuclear pores
Regulate transport of RNA and proteins into and out of nucleus
Traffic is FAST! 1 typical human cell has to import 560,000 ribosomal proteins/minute, export 14,000 assembled ribosomes/minute
Small molecules and proteins of less than 9 nm can pass freely
Large proteins must be assisted
Nuclear pores act as turnstiles

26. Nuclear Localization Signal (NLS)
-Pro-Pro-Lys-Lys-Lys-Arg-Lys-Val-

27. What happens when we alter the NLS?
Kalderson, Roberts, Richardson, Smith (1984) Cell 39:p499.
mutation

28. Another Experiment Microinjection Pipettes
What happens when we use recombinant DNA techniques to
add the NLS to a dummy protein?
Normal or modified Bovine Serum Albumin (NLS added) and injected to the cytoplasm
Microinjection Pipettes
Normal BSA
BSA with NLS

29. So What? This provided evidence of nuclear transport receptors
family of proteins associated with the nuclear pore complex
Importins recognize the NLS and bring proteins in
Another set of proteins, the exportins, work in the opposite direction (These recognize other signals)

31. 15_09_pore_transport.jpg
NLS
15_09_pore_transport.jpg

34. 15.4

37. L’involucro nucleare è disassemblato durante la mitosi