Cholesterol auxotrophic cells are unable to produce their own cholesterol so they must rely on LDL present in the cell culture media. Please briefly describe three different ways that can be used to create a cholesterol auxotrophic cell line.

The three methods are: 1) Using H-Ras- SREBP- 2 Fusion proteins, the NH2 segment can be released by two sequentia

Explanation:

Sterol regulatory element binding proteins (SREBPs) are transcription factors attached to the endoplasmic reticulum. The NH2-segment, which activates transcription, is connected to membranes by a hairpin anchor formed by two transmembrane sequences and a short lumenal loop. Using H-Ras–SREBP-2 fusion proteins, we show that the NH2-segment is released from membranes by two sequential cleavages. The first, regulated by sterols, occurs in the lumenal loop. The second, not regulated by sterols, occurs within the first transmembrane domain. The liberated NH2-segment enters the nucleus and activates genes controlling cholesterol synthesis and uptake. Certain mutant Chinese hamster ovary cells are auxotrophic for cholesterol because they fail to carry out the second cleavage; the NH2-segment remains membrane-bound and transcription is not activated.

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answer:

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explanation:

08: 21

read the excerpt from "the tell-tale heart.”

object there was none. passion there was none. i loved the old man. he had never wronged me. he had never given me insult. for his gold i had no desire. i think it was his eye! yes, it was this! he had the eye of a vulture—a pale blue eye, with a film over it. whenever it fell upon me, my blood ran cold; and so by degrees—very gradually—i made up my mind to take the life of the old man, and thus rid myself of the eye forever.  

read the excerpt from "the black cat.”

beneath the pressure of torments such as these, the feeble remnant of the good within me succumbed. evil thoughts became my sole intimates—the darkest and most evil of thoughts. the moodiness of my usual temper increased to hatred of all things and of all mankind; while, from the sudden, frequent, and ungovernable outbursts of a fury to which i now blindly abandoned myself, my uncomplaining wife, alas! was the most usual and the most patient of sufferers.

by revealing the narrator’s deepest thoughts, the author