Beta1,4-galactosyltransferase and lactose biosynthesis: recruitment of a housekeeping gene from the nonmammalian vertebrate gene pool for a mammary gland specific function.
J Mammary Gland Biol Neoplasia
; 3(3): 315-24, 1998 Jul.
Article
in En
| MEDLINE
| ID: mdl-10819517
ABSTRACT
Beta1,4-galactosyltransferase (beta4GalT-I) is a constitutively expressed trans-Golgi enzyme, widely distributed in vertebrates, which synthesizes the beta4-N-acetyllactosamine structure commonly found in glycoconjugates. In mammals beta4GalT-I has been recruited for a second biosynthetic function, the production of lactose; this function takes place exclusively in the lactating mammary gland. In preparation for lactose biosynthesis, beta4GalT-I enzyme levels are increased significantly. We show that mammals have evolved a two-step mechanism to achieve this increase. In step one there is a switch to the use of a second transcriptional start site, regulated by a stronger, mammary gland-restricted promoter. The transcript produced is distinguished from its housekeeping counterpart by the absence of approximately 180 nt of 5'-untranslated sequence. In step two, this truncated transcript is translated more efficiently, relative to the major transcript expressed in all other somatic tissues.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Vertebrates
/
Lactose Synthase
/
Gene Pool
/
Lactose
/
Mammary Glands, Animal
Limits:
Animals
/
Female
/
Humans
Language:
En
Journal:
J Mammary Gland Biol Neoplasia
Journal subject:
NEOPLASIAS
Year:
1998
Document type:
Article
Affiliation country: