Josh: This is pure speculation, but perhaps this was introduced from viruses. The article states that the hammerhead ribozyme was previously only believed to be found in plant viruses, but they are probably also found in other viruses. Mammals inherited a lot of techniques used for gene regulation from viruses or defense from viruses (such as microRNAs).

Researchers at the University of California, Santa Cruz, have discovered a type of gene regulation never before observed in mammals–a “ribozyme” that controls the activity of an important family of genes in several different species.

The findings, published July 9 in the journal Nature, describe a new and surprising role for the so-called hammerhead ribozyme, an unusual molecule previously associated with obscure virus-like plant pathogens called viroids. The UCSC researchers found the ribozyme embedded within certain genes in mice, rats, horses, platypuses, and several other mammals. The genes are involved in the immune response and bone metabolism. … Continue Reading »