The enzyme that uses one strand of DNA as a template to assemble nucleotides into RNA is RNA polymerase.

Here's a breakdown:

* RNA polymerase is a key enzyme in the process of transcription, where genetic information from DNA is copied into RNA.

* Transcription is the first step in gene expression, and it's essential for protein synthesis and other cellular processes.

* RNA polymerase binds to the DNA template strand and reads the sequence of nucleotides.

* It then uses this information to assemble a complementary RNA molecule, following the base pairing rules (A with U, C with G).

* The resulting RNA molecule is a faithful copy of the DNA template sequence, but it contains uracil (U) instead of thymine (T).

Let me know if you have any more questions!