Transcription Factors and Machinery in RNA Synthesis

Subnuclear structures populate the nucleus.

Although the nucleolus is the most prominent nuclear body, others have been studied. Cajal bodies (named for the scientist who first described them in 1906), GEMS, and interchromatin granule clusters (also called “speckles”) Like the nucleolus, these other nuclear structures lack membranes and are highly dynamic. Their appearance is likely due to the tight association of protein, RNA, and DNA components involved in gene expression. Cajal bodies and GEMS are often paired in the nucleus; it’s unclear if they are distinct structures. They may be where snRNAs and snoRNAs assemble with protein. RNAs and proteins that make up snRNPs are partially assembled in the cytoplasm but modified in the nucleus. Cajal bodies/GEMS may be where snRNPs are recycled and their RNAs “reset” after splicing rearrangements. Interchromatin granule clusters may store fully mature snRNPs for pre-mRNA splicing.

From DNA to RNA and beyond

The genetic instructions that are contained in a cell’s genes can only be read out, or expressed, through the processes of transcription and translation. Cells are able to rapidly produce a large quantity of protein when it is necessary to do so due to the fact that a single gene can produce a large number of copies of identical RNA, and each RNA molecule can direct the synthesis of a large number of identical protein molecules. However, the transcription and translation of each gene can take place with varying degrees of efficiency, enabling the cell to produce vast quantities of some proteins while producing only trace amounts of others (Figure 6-3). In addition, as we will see in the following chapter, a cell is able to alter (or regulate) the expression of each of its genes in response to the requirements of the current environment, most obviously through the regulation of the production of its RNA.

It’s possible for genes to express themselves in a variety of ways. Gene A’s transcription and translation processes are significantly more efficient than gene B’s. Because of this, the amount of protein A that is found in the cell can be significantly higher than the amount of protein B.

DNA Converted Into RNA.

In order for a cell to read out a necessary portion of its genetic instructions, the cell must first copy a specific section of its DNA nucleotide sequence, known as a gene, into an RNA nucleotide sequence. This is the first step in the process. Although the information in RNA has been copied into a different chemical form, it is still written in essentially the same language as it is in DNA. This language is known as the language of a nucleotide sequence. Because of this, the name was transcribed.

RNA is also a linear polymer, but unlike DNA, it is composed of four distinct types of nucleotide subunits that are linked to one another by phosphodiester bonds. The nucleotides in RNA are ribonucleotides, which means that they contain the sugar ribose (hence the name ribonucleic acid) rather than deoxyribose. Additionally, while RNA, like DNA, contains the bases adenine (A), guanine (G), and cytosine (C), it also contains the base uracil (U) rather than the base thymine (T), which is found The complementary base-pairing properties that were discussed in Chapters 4 and 5 for DNA also apply to RNA. This is because U, like T, can form a base pair with A through the process of hydrogen bonding (in RNA, G pairs with C, and A pairs with U). On the other hand, it is not unheard of to discover other types of base pairs in RNA; for instance, G pairing with U could happen on occasion.

RNA’s molecular make-up from a chemical standpoint. 

(A) RNA is made up of the sugar known as ribose, which is distinct from the sugar known as deoxyribose, which is used in DNA, because it contains an additional -OH group.

(B) RNA has the base uracil, which is dissimilar to the base thymine, which serves the same function in DNA 

Uracil and adenine can form base pairs. Adenine and uracil can combine to form base pairs. Due to the fact that the absence of a methyl group in U has no impact on base-pairing, U-A base pairs are very similar to T-A base pairs.

Conclusion

Transcription is required before protein synthesis can begin. Bacteria have one RNA polymerase (the enzyme that carries out the transcription of DNA into RNA). This enzyme initiates transcription at a promoter, synthesises RNA by chain elongation, stops transcription at a terminator, and releases the DNA template and mRNA. In eukaryotic cells, transcription is more complex, with three RNA polymerases related evolutionarily to each other and to the bacterial polymerase.