Transcription, definition

Many aspects relating to the specificity and intensity of gene transcription in response to hormones remain open. Nevertheless, a prudent conclusion permits establishing that two definite elements are intervening the interaction of the receptor dimer with the palindrome and several protein-protein interactions that are produced between the dimer and the remaining components of the transcription machinery (Beato 1989). 

Apo(a) isoform size variability was subsequently found to result from differences in sizes of the hepatic apo(a) mRNA in both humans (K25) and baboons (H31) with few exceptions, apo(a) protein sizes were directly correlated to the size of the apo(a) transcript. Although studies suggested differences in the numbers of kringle IV repeats in the gene (G8, LI9), size variation in the apo(a) gene was definitively shown to result from differences in the number of tandemly... 

Clearly, the results emerging suggested that at least two nucleotides were modified, the absolute sequence position within the tRNA had yet to be established. Ching etalP showed that a Se U residue was present in the wobble position of the tRNA " from C. sticklandii. This study confirmed a notion that the modification probably affects the translation efficiency of certain transcripts, based on the level of modification by selenium. The authors speculated that the modification to seleno-tRNA (GAG) allowed for more efficient use of this tRNA species as compared to the tRNA (GAA). Even today, no definitive data exist to show that this modification alters the translation efficiency in these bacterial model systems. Nonetheless, these studies had established the chemical forms of Se U and mnm Se U, and established that they were derived from modifications to nucleotides that first required sulfur (S U and mnm S U), the mechanism by which selenium was inserted into the tRNA would not be definitively answered until many years later. 

A stretch of DNA that is transcribed as a single continuous RNA strand is called a transcription unit. A unit of transcription may contain one or more sequences encoding different polypeptide chains (translational open reading frames, ORF) or cistrons. The transcription unit is sometimes termed the primary transcript, pre-messenger RNA or heterogeneous nuclear RNA (hnRNA). The primary transcript is further processed to produce mRNA in a form that is relatively stable and readily participates in translation. In order to understand the primary need for processing of this RNA, the biochemical definition of a gene must be discussed. 

Ishov, A.M., Stenberg, R.M., and Maui, G.G. (1997) Human cytomegalovirus immediate early interaction with host nuclear structures definition of an immediate transcript environment. J. Cell. Biol. 14 138(1), 5-16. 

It is generally true that that eucaryotic transcriptional activators act via direct or indirect protein-protein contacts with the transcription apparatus. In this context the definition of the transcription apparatus is rather broad it includes the basal apparatus as well as proteins which act as co-activators or mediators (see 1.4.3.2). 

At the cytogenetic level, resistance can be defined as a loss or lack of MCR or CCR. At the molecular level, a complete molecular response is defined as undetectable BCR-ABLl transcripts by PCR or a > 3-log reduction, a BCR-ABLl transcripts which represents a major molecular remission. Loss of either of these responses would be defined as resistance at the molecular level. However, standardization of measurement of BCR-ABLl transcripts by PCR has not yet been accomplished, and results in one lab may not necessarily be equivalent to those of another lab. Also, a standardized definition of resistance at the molecular level is not well defined, although many experts consider a half log or one-log increase which is confirmed in a second sample as a reasonable benchmark for loss of molecular response (27). 

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