The same convention is used for proteins, they can be named domains of unknown function (DUFs).
RNA | 16S ribosomal RNA | RNA polymerase | Tomb of the Unknown Soldier | Out of the Unknown | Green function | Graph of a function | RNA polymerase II | Hash function | Schur function | RNA-dependent RNA polymerase | Riemann zeta function | Dirac delta function | Bessel function | Challengers of the Unknown | RNA virus | RNA interference | RNA-binding protein | Unknown Pleasures | non-coding RNA | Monotonic function | Lateralization of brain function | function (mathematics) | Cryptographic hash function | Transfer RNA | The Unknown Warrior | RNA-Seq | RNA polymerase III | RNA polymerase I | Persons Unknown (TV series) |