Illustration of the 7SK core ribonucleoprotein (RNP) complexed with a circular RNA (ribonucleic acid). 7SK regulates RNA polymerase II, the enzyme that synthesises a complementary mRNA (messenger ribonucleic acid) strand from a strand of DNA (deoxyribonucleic acid) during a process called transcription. 7SK is hijacked by HIV particles when they infect a cell for viral transcription and replication.