<P> Transcription termination has also emerged as an important area of transcriptional regulation . Termination is coupled with the efficient recycling of polymerase . The factors associated with transcription termination can also mediate gene looping and thereby determine the efficiency of re-initiation . </P> <P> When transcription is arrested by the presence of a lesion in the transcribed strand of a gene, DNA repair proteins are recruited to the stalled RNA polymerase to initiate a process called transcription - coupled repair . Central to this process is the general transcription factor TFIIH that has ATPase activity . TFIIH causes a conformational change in the polymerase, to expose the transcription bubble trapped inside, in order for the DNA repair enzymes to gain access to the lesion . Thus, RNA polymerase serves as damage - sensing protein in the cell to target repair enzymes to genes that are being actively transcribed . </P> <P> Eukaryotic transcription is more complex than prokaryotic transcription . For instance, in eukaryotes the genetic material (DNA), and therefore transcription, is primarily localized to the nucleus, where it is separated from the cytoplasm (in which translation occurs) by the nuclear membrane . This allows for the temporal regulation of gene expression through the sequestration of the RNA in the nucleus, and allows for selective transport of mature RNAs to the cytoplasm . Bacteria do not have a distinct nucleus that separates DNA from ribosome and mRNA is translated into protein as soon as it is transcribed . The coupling between the two processes provides an important mechanism for prokaryotic gene regulation . </P> <P> At the level of initiation, RNA polymerase in prokaryotes (bacteria in particular) binds strongly to the promoter region and initiates a high basal rate of transcription . No ATP hydrolysis is needed for the close - to - open transition, promoter melting is driven by binding reactions that favor the melted conformation . Chromatin greatly impedes transcription in eukaryotes . Assembly of large multi-protein preinitiation complex is required for promoter - specific initiation . Promoter melting in eukaryotes requires hydrolysis of ATP . As a result, eukaryotic RNA polymerases exhibit a low basal rate of transcription initiation . </P>

Name two essential features or functions of the core promoter in eukaryotes