<Li> Ribosomal RNA (rRNA)--a component of ribosomes </Li> <Li> Micro RNA--regulates gene activity </Li> <Li> Catalytic RNA (Ribozyme)--enzymatically active RNA molecules </Li> <P> RNAP accomplishes de novo synthesis . It is able to do this because specific interactions with the initiating nucleotide hold RNAP rigidly in place, facilitating chemical attack on the incoming nucleotide . Such specific interactions explain why RNAP prefers to start transcripts with ATP (followed by GTP, UTP, and then CTP). In contrast to DNA polymerase, RNAP includes helicase activity, therefore no separate enzyme is needed to unwind DNA . </P>

Where is rna polymerase found in the cell