Those are actually leaderless mRNAs, and they are very common in many species of bacteria, archaea, and human mitochondria. 5' AUG can be threaded into the P-site of 70S ribosomes where it can pair with fmettRNAfMet. Here's a great review: doi: 10.1128/microbiolspec.RWR-0016-2017. PMID: 30006995