MEIOTIN-1 - THE MEIOSIS READINESS FACTOR

Meiotin-1 is a protein found in developing microsporocytes of Lilium l ongiflorum, and immunological assays indicate that cognates exist in b oth mono-and dicotyledonous plants. Its temporal and spatial expressio n pattern, coupled with its unusual distribution in chromatin and the properties it shares with histone H1, encourages speculation that it i s involved in regulating meiotic chromatin structure. Molecular analys es provide support for the hypothesis that meiotin-1 arose from histon e H1 by an exon shuffling mechanism, as meiotin-1 is an H1-like protei n that lacks the amino-terminal domain shared by H1 molecules, We have proposed that meiotin-1 serves to limit chromatin condensation in ord er to foster the unique cytological and molecular events which occur d uring meiotic prophase. As such, meiotin-1 fits the role of a 'meiosis readiness factor', and its accumulation to a threshold level may comm it mitotically dividing progenitor cells to differentiate into meiocyt es.