Chapter 8 Nucleus and chromosomes Learning Objectives (1)A typical nonmitotic nucleus includes several major components. (2) Nuclear envelope and nuclear pore complex. (3)The components of chromatin and packaging of chromosome (4) Nucleolus
Nucleus and Chromosomes Chapter 8 Learning Objectives (1) A typical nonmitotic nucleus includes several major components. (2) Nuclear envelope and nuclear pore complex. (3) The components of chromatin and packaging of chromosome. (4) Nucleolus
1. The nucleus: Nuclear envelope and npc A. Structure: Double-membrane nuclear envelope surrounds the nucleus Nuclear lamina lucien enve nner nuclear Nucleolus embrane Chromatin Perinuclear space SeNUCLEOPLAS Figure 16-26 The Structural Organization of the Nucleus and Nuclear pores Nuclear Envelope. (a) An electron micrograph of the nucleus frum a mouse liver cell, with prominent structutal features labeled(TEM The CYTOSOL nuclear envelope is a doutle membrane perforated ty iclear pores INP) Internal structures include the nucleolus nu), euchromatin (eu), and heterochromatin (he).(b)A drawing of a typical nucleus Structural Rough ER features included here but not visible in he micrograph include the nuclear lamina niosomes on the outer nuclear membrane. and the continuity between the outer nuclear membrane and the rough ER
1. The nucleus: Nuclear envelope and NPC A. Structure: Double-membrane nuclear envelope surrounds the nucleus
B. The nuclear envelope consists consists of two membranes by a perinuclear space. The inner surface of the nuclear envelope is lined by the nuclear lamina > The nuclear lamina supports the nuclear envelope: Gives shape and stability of nuclear envelope: Provides a structure link between chromatin and nuclear envelope > The nuclear lamina is composed of lamins >The integrity of the nuclear lamina is regulated by phosphorylation and dephosphorylation
B. The nuclear envelope consists consists of two membranes by a perinuclear space. ❖The inner surface of the nuclear envelope is lined by the nuclear lamina ➢The nuclear lamina supports the nuclear envelope: Gives shape and stability of nuclear envelope; Provides a structure link between chromatin and nuclear envelope ➢The nuclear lamina is composed of lamins. ➢The integrity of the nuclear lamina is regulated by phosphorylation and dephosphorylation
nucloar pore lamins DNA inner nuclear membrane nuclear envelope outer nuclear membrane nuclear pore PHOSPHORYLA complex proteins FUSION OF ENVELOPED CHROMOSOMES phosphorylated INTERPHASE NUCLEUS P chromatid nuclear envelope somOsomo fragment LATE TELOPHASE PROPHASE DEPHOSPHORYLATION FUSION OF NUCLEAR OF LAMINS ENVELOPE FRAGMENTS EARLY TELOPHASE Breakdown and reformation of nuclear envelope during mitosis
Breakdown and reformation of nuclear envelope during mitosis
>The phosphorylation of the lamins triggers the disassembly of the nuclear lamina, which in turn cause the nuclear envelope to break up into vesicles phosphorylation of the lamins helps reverse the process. >Because the new nuclear envelope is so closely applied to the surface of the chromosomes. it excludes all of the proteins in the cell except those bound to the chromosomes. So nuclear localization signals are not cleaved off after transport into the nucleus Old nuclear envelope reforms new nuclear envelope
➢The phosphorylation of the lamins triggers the disassembly of the nuclear lamina, which in turn cause the nuclear envelope to break up into vesicles. Dephosphorylation of the lamins helps reverse the process. ➢Because the new nuclear envelope is so closely applied to the surface of the chromosomes, it excludes all of the proteins in the cell except those bound to the chromosomes. So nuclear localization signals are not cleaved off after transport into the nucleus. ➢Old nuclear envelope reforms new nuclear envelope