细胞科学 el Science 蔡国平
细胞科学 Cell Science （11） 蔡国平
8 11. The cell nucleus and the control of gene expression 1. Outline 2. The nuclear envelope 3. The nucleolus 4 The chromatin and chromosomes 5. The nucleus as an organized organelle 6: The complex of eukaryote genome 7. Control of gene expression in karyotes
§11. The cell nucleus and the control of gene expression 1. Outline 2. The nuclear envelope 3. The nucleolus 4. The chromatin and chromosomes 5. The nucleus as an organized organelle 6. The complex of eukaryote genome 7. Control of gene expression in karyotes
DNA and associated proteins(chromatin) endoplasmIc reticulum ucleolu l centro osome microtubule intermediate filaments nuclear lamina nuclear pore outer nuclear membrane nuclear envelope inner nuclear membrane
11.1. Outline The nucleus is the biggest and most important organelle of the cell. The presence of the nucleus is the principal feature that distinguishes eukaryotic from prokaryotic cells, Almost eukaryotic cells have the nucleus except mature red blood cells of mammals and sieve cells of high plants etc. By housing the cells genome, the nucleus serves both as the repository of genetic information and as the control center of cellular inheritance and metabolisms. From a fertilized egg the complete set of genetic instructions are faithfully replicated and distributed to each cell of a developing organism. However, for each different cell with the completely same genetic blueprints, there are also the programs and mechanism by which the blueprints are selectively put into effect at different cells at particular
11.1. Outline The nucleus is the biggest and most important organelle of the cell. The presence of the nucleus is the principal feature that distinguishes eukaryotic from prokaryotic cells, Almost eukaryotic cells have the nucleus except mature red blood cells of mammals and sieve cells of high plants etc.. By housing the cell’s genome, the nucleus serves both as the repository of genetic information and as the control center of cellular inheritance and metabolisms. From a fertilized egg the complete set of genetic instructions are faithfully replicated and distributed to each cell of a developing organism. However, for each different cell with the completely same genetic blueprints, there are also the programs and mechanism by which the blueprints are selectively put into effect at different cells at particular
N 间 Animal cell nucleus (b) Plant cell nucleus Figure 16-25 The Nucleus. The nucleus is a prominent structural secretory granules (SG) in the cytoplasm. (b) The nucleus(N)of a plant feature in most eukaryotic cells. (a) The nucleus IN of an animal cell. This cell. This is a cell from a soybean root nodule. The prominence af plastids s an insulin-producing cell from a rat pancreas: hence, the prominence of P)reflects their role in the storage of starch granules (TEMs)
Outer nucl membran Nuclear lam Nuclear envel her nuclear Perinuclear space Ribosomes Figure 16-26 The Structural Organization of the Nucleus and Nuclear pores Nuclear Envelope. (a) An electron micrograph of the nucleus from a mouse liver cell, with prominent structural features labeled (TEM). The CYTOSO nuclear envelope is a double membrane perforated by nuclear pores(NP Internal structures include the nucleolus (nu), euchromatin (eu), and heterochromatin (hek. (b) A drawing of a typical nucleus Structural Rough ER features included here but not visible in the micrograph include the nuclear lamina, ribosomes on the outer nuclear membrane, and the continuity between the outer nuclear membrane and the rough ER
time, determining differentiation, growth, proliferation metabolism and behaviors as well as apoptosis of the cell Actually, DNA replication, transcription, and RNA processing all take place within the nucleus, with only the final stage of gene expression(translation) localized to the cytoplasm. The presence of the nucleus provides opportunities for the control of gene expression at the level of transcription, such as by the regulated transport of transcription factors, and allows gene expression to be regulated by posttranscriptional mechanism, such as alternative splicing. The separation of the genome from the site of mRNa translation thus plays a central role in eukaryotic gene expression
time, determining differentiation, growth , proliferation, metabolism and behaviors as well as apoptosis of the cell. Actually, DNA replication, transcription, and RNA processing all take place within the nucleus, with only the final stage of gene expression (translation) localized to the cytoplasm. The presence of the nucleus provides opportunities for the control of gene expression at the level of transcription, such as by the regulated transport of transcription factors, and allows gene expression to be regulated by posttranscriptional mechanism, such as alternative splicing. The separation of the genome from the site of mRNA translation thus plays a central role in eukaryotic gene expression
1) Morphology形态 细胞核多是圆形或椭圆形,但是也有其它形态的细胞核如多形核白 细胞的核呈多瓣形;蚕丝腺泡细胞的核为分枝形,方便信息传递,有 利于丝蛋白合成;高等植物的胚乳细胞的核有时呈网状。 2)size大小 不同的细胞的细胞核大小差异很大,从小至l大到数百μ不等,苏铁 科植物的卵细胞的核达500-600μ。影响细胞核大小的主要因素是核/质 体积比(通常约为1/3),如10-30μ大小的肝细胞的细胞核约为7μ, 高等动物约5-10μ,低等植物约1-4μu,而高等植物约5-20μ。在细胞发 育的不同时期,核质比会发生变化以满足功能的需要。如植物分生组 织核/质比随着发育由0.5逐渐变小 3) Numbers数目 细胞通常仅有一个细胞核,但是,有的细胞可能含有两个或更多的 核。植物毡绒层细胞有2-4个核,低等植物藻类的细胞核有几个甚至 几十个。某些动物细胞在某个发育阶段特别在胚胎发育期会出现多核 现象,如常见的共质体或合胞体。 4) Location定位 细胞核多位于细胞中央,但是,也有不同的定位,上皮细胞的细胞 核偏于基底一侧,植物细胞则被巨大的液泡挤到一边
1) Morphology 形态 细胞核 多是圆形或椭圆形，但是也有其它形态的细胞核 如多形核白 细胞的核呈多瓣 形；蚕丝腺泡细胞的核为分枝形，方便信息传递，有 利于丝蛋白合成；高等植物的胚乳细胞的核有时呈网状。 2) size大小 不同的细胞的细胞核大小差异很大， 从小至1 大到数百不等，苏铁 科植物的卵细胞的核达500-600 。影响细胞核大小的主要因素是核/质 体积比（通常约为1/3），如10-30 大小的肝细胞的细胞核约为7 ， 高等动物约5-10 ，低等植物约1-4 ，而高等植物约5-20 。在细胞发 育的不同时期，核/质比会发生变化以满足功能的需要。如植物分生组 织核/质比随着发育由0.5逐渐变小. 3) Numbers数目 细胞通常仅有一个细胞核， 但是，有的细胞可能含有两个或更多的 核。 植物毡绒层细胞有2-4个核， 低等植物藻类的细胞核有几个甚至 几十个。某些动物细胞在某个发育阶段特别在胚胎发育期会出现多核 现象，如常见的共质体或合胞体。 4) Location定位 细胞核多位于细胞中央，但是，也有不同的定位， 上皮细胞的细胞 核偏于基底一侧，植物细胞则被巨大的液泡挤到一边
5) Basic structure of nucleus细胞核的基本结构 细胞核在细胞周期中呈现两种不同的状态或者说处 于两个阶段,即间期核 nucleus during interphase,呈 现典型完整的核形态,而分裂相核 nucleus during mitosis,其核膜消失,核质混合。以下介绍的是间期 核的结构.间期核呈现为粘稠的无定形的物质被核被膜 所包围, 主要有五个结构成分: (1)核被膜 the nuclear envelope(NE)-以两层平行的单 位膜为核心的复杂结构 (2)核仁the e nucleolus (nucleo i)-细胞核含有一个或多 个核仁,呈电子密度大的无定形结构,其功能为合成 rRNA和核糖体大亚基的装配
5) Basic structure of nucleus 细胞核的基本结构 细胞核在细胞周期中呈现两种不同的状态或者说处 于两个阶段，即间期核 nucleus during interphase ，呈 现典型完整的核形态， 而分裂相核nucleus during mitosis，其核膜消失，核质混合。以下介绍的是间期 核的结构. 间期核呈现为粘稠的无定形的物质被核被膜 所包围, 主要有五个结构成分： (1)核被膜 the nuclear envelope (NE)- 以两层平行的单 位膜为核心的复杂结构. (2)核仁 the nucleolus (nucleoli)- 细胞核含有一个或多 个核仁, 呈电子密度大的无定形结构, 其功能为合成 rRNA和核糖体大亚基的装配
(3)染色质 he chromatin-极为伸展的核蛋白质丝 (4)核基质 the nuclear matrix-蛋白丝状网络( protein- containing fibrillar network) (5)核液 the nucleoplasm fluid-含有蛋白质,核酸,核苷酸 及无机离子等的胶体溶液,必须指出核液是执行核功 的必不可少的生物化学环境.例如, small molecular nuclear rna( SnRNas),除了v3 SnrNas(U1-U6),均存 在于核液,所形成的 SnRNP在RNA的加工方面起重要作 用核液含有功能尚不清楚的小分子 class ii rna Recent advances in understanding a small GTPase of the Ras super family, Ran have shown that it has a central role in the control of ne dynamics and nuclear transport, as well as mitotic spindle assembly. It was proposed that ran GTP might act as a molecular marker, which distinguishes the nucleoplasm from the cytoplasm
(3)染色质the chromatin- 极为伸展的核蛋白质丝. (4) 核基质the nuclear matrix-蛋 白丝状网络(proteincontaining fibrillar network) (5)核液 the nucleoplasm fluid -含有蛋白质,核酸, 核苷酸 及无机离子等的胶体溶液, 必须指出核液是执行核功能 的必不可少的生物化学环境. 例如, small molecular nuclear RNA（snRNAs), 除了v3 snRNAs (U1 -U6 ) ，均存 在于核液, 所形成的snRNP在RNA的加工方面起重要作 用.核液 含有功能尚不清楚的小分子 class III RNA. Recent advances in understanding a small GTPase of the Ras superfamily, Ran have shown that it has a central role in the control of NE dynamics and nuclear transport, as well as mitotic spindle assembly.It was proposed that RanGTP might act as a molecular marker,which distinguishes the nucleoplasm from the cytoplasm