This study aims to investigate a specific construction in spoken discourse, i.e. that's (not) the bottom line is (that) and its variant forms, in recent American English. The function of the bottom line is (that) is for a speaker to introduce or anticipate upcoming talk, while that's the bottom line allows a speaker to summarize his/her preceding statement. These constructions give rise to a new construction when repeatedly used in the following sequence: anaphoric that's (not) the bottom line followed by cataphoric the bottom line is (that). The newly emerging construction, i.e. that's (not) the bottom line is (that), is an "apo-koinou" construction, which consists of two clauses which have a word or phrase in common. The remainder of the study then discusses how the notions of "constructional change", "constructionalization", and "constructional expansion" may be applied to the individual SN-constructions and to the resulting apo-koinou constructions.