How many basal transcription factors are there

In mice, the expression of Tbp2 mRNA has been detected specifically in the oocytes [ 4 , 9 ]. Although there is controversy regarding the specificity of this expression, a recent genetic study indicated that the main role of TBP2 is restricted to the female germline [ 3 , 10 ] and references therein. TBP2 protein accumulates in the nuclei of growing mouse oocytes during folliculogenesis, and its level declines on ovulation to become undetectable after fertilization [ 10 ] Figure 1.

In contrast, TBP is expressed in the oocytes only at the beginning of folliculogenesis and after fertilization, but not during oocyte growth [ 10 ] Figure 1. However, females lacking TBP2 are sterile as a result of defective folliculogenesis. A general decrease in transcription is indicated by the reduced phosphorylation on serine 2 of Pol II and reduced methylation of histone H3 lysine 4, which are markers of active genes.

In contrast, when TBP2 is misexpressed in early mouse embryos, where it is normally not expressed, it has a negative effect on cell proliferation, leading to developmental arrest [ 6 ]. These data together demonstrate that TBP2 is not required for mouse viability but has a critical and specialized role in mammalian female germ cell development, and they provide evidence for non-redundant functions of TBP2 and TBP in vivo in the mouse.

The observations from frogs and mice [ 5 , 6 ] clearly establish TBP2 as an oocyte-specific TBP-type factor in vertebrates. In both organisms during certain stages of oocyte development, TBP is absent and dispensable Figure 1. Thus, the unique role of TBP2 in oocyte transcription, in a highly specialized cell type, provides evidence that the basal transcription machinery is highly flexible and can switch factors depending on the cellular and ontogenic requirements.

A common model for subfunctionalization of TBP and TBP2 during the transition between oocyte and embryo is thus emerging from two evolutionarily distant vertebrates, although there remain important lineage-specific differences between them. In anamniotes, TBP2 proteins mostly although not completely degrade before the embryo is formed [ 5 ].

In contrast to mammals, a large amount of TBP mRNA is produced maternally and seems to be prevented from being translated in the oocyte and the early embryo. To achieve factor switching, the maternal TBP mRNA translation is activated before global zygotic gene activation to generate an abundant pool of TBP protein, thereby becoming the dominant factor in the embryo.

The question remains: why is there a distinct requirement for either of the two TBP paralogs in oocytes and embryos? Alternatively, the amino-terminal domain of TBP2 could function to regulate the DNA binding function of the carboxy-terminal domain, or to regulate protein dynamics, which as suggested by Akhtar and Veenstra [ 5 ] involves regulation of protein degradation.

In summary, a protein very similar to TBP seems to have evolved by gene duplication and has a non-redundant regulatory function in transcription initiation in the vertebrate oocyte.

Further investigations are required to address how TBP2 functions in the oocyte and what specific properties and molecular mechanisms of transcription initiation distinguish the oocyte from the soma and the embryo. Juven-Gershon T, Kadonaga JT: Regulation of gene expression via the core promoter and the basal transcriptional machinery.

Dev Biol. Google Scholar. These factors are either associated directly with RNA Polymerase or add in building the actual transcription apparatus. The general term for these associated proteins is transcription factor. Transcription factor - any protein other than RNA Polymerase that is required for transcription Functions of Transcription Factors bind to RNA Polymerase bind another transcription factor bind to cis-acting DNA sequences RNA Polymerase and the group of protein that directly interact with it are called the basal transcription apparatus.

This shape change allows for the interaction of the specific activator proteins bound to the enhancers with the general transcription factors bound to the promoter region and the RNA polymerase. Figure 1. An enhancer is a DNA sequence that promotes transcription. Each enhancer is made up of short DNA sequences called distal control elements. Activators bound to the distal control elements interact with mediator proteins and transcription factors.

Two different genes may have the same promoter but different distal control elements, enabling differential gene expression. Like prokaryotic cells, eukaryotic cells also have mechanisms to prevent transcription. Transcriptional repressors can bind to promoter or enhancer regions and block transcription.

Like the transcriptional activators, repressors respond to external stimuli to prevent the binding of activating transcription factors. The binding of additional regulatory transcription factors to cis -acting elements will either increase or prevent transcription. In addition to promoter sequences, enhancer regions help augment transcription. Enhancers can be upstream, downstream, within a gene itself, or on other chromosomes.

Transcription factors bind to enhancer regions to increase or prevent transcription. A mutation within the promoter region can alter transcription of a gene. Hua 50 and tomato Solanum lycopersicum L. The Xoc strain RH3 is also frequently used in research Yuan et al. Xcc strain X Fu et al.

For stable transformation of rice, Agrobacterium- mediated transformation was performed using calli derived from mature embryos of indica rice line IRBB5 according to previously reported methods Ge et al.

For transiently suppressing the target gene in sweet orange, Xcc -facilitated agroinfiltration was performed. Eight hours later, the same inoculated leaf areas were subjected to agroinfiltration with Agrobacterium carrying the recombinant construct Hu et al. For transiently suppressing target gene in pepper and tomato, virus-induced gene silencing VIGS was performed. The recombinant vectors were introduced into GV Agrobacterium culture was infiltrated into the cotyledons of germinating pepper plants or the first two true leaves of the four-leaf stage tomato plants using a 1-ml needleless syringe Liu et al.

Agrobacterium -mediated transformation was performed by infiltrating into Nicotiana benthamiana leaves using a needleless syringe. Each CoIP assay was repeated at least twice. The original western blotting images are provided in Supplementary Figure The mutagenic primers are listed in Supplementary Table 1. To evaluate rice bacterial blight disease, rice plants were inoculated with Xoo by the leaf-clipping method at the booting panicle development stage Chen et al.

Disease was scored by measuring the lesion length at 14 days after inoculation. To evaluate rice bacterial streak disease, rice plants were inoculated with Xoc strains by the needle stab method at the tillering stage Yuan et al. The disease was scored by measuring the lesion length at 14 days after inoculation. The bacterial growth rate in sweet orange leaves was measured by counting the cfu as described previously Hu et al.

The bacterial growth rate in pepper or tomato leaves was measured by counting the cfu as described previously Bonas et al. For gene expression analysis, 2-cm rice leaf fragments near the bacterial infection sites or citrus, pepper and tomato leaf tissues next to the infiltration sites were collected for RNA isolation.

The expression level of rice, pepper or tomato actin gene or citrus EF1a gene was used to standardize the RNA sample of rice, pepper, tomato or citrus, respectively. The expression level relative to that of controls was assessed. Each qRT-PCR assay was repeated at least twice with similar result, with each repetition having three replicates.

Xcc causes citrus canker. The interactions were assessed by growth of yeast cells on synthetic defined premixes SD medium lacking leucine L , tryptophan W , histidine H , and adenine A.

E Thin cross-section images of leaves at 14 days after inoculation with Xcc. All the citrus species were similarly susceptible to Xcc Supplementary Figure 2B. The Oryza genus consists of two cultivated rice species, Asian cultivated rice O. Thus the O.

The V type occurs in plants O. The L type occurs in animals Rattus norvegicus, Homo sapiens, Danio rerio , and Drosophila melanogaster. These transgenic plants also showed increased susceptibility to Xoo and Xoc , which was associated with increased induced expression of rice susceptibility genes, compared to wild-type plants Supplementary Figures 4, 5.

T1 plants were inoculated with Xoo at the booting stage and Xoc at the tillering stage. Actin transcripts were detected as control. We also examined the relationship between pepper Capsicum annuum L.